V'  ■'.■::■■  ■ 

BRARY  FACItlTY 
1   ill  III    III 

It'.    ' 

1 

THE 

CONSTRUCTION  OF  LOMBARi. 

AND  GOTHIC  VAULTS 


By  ARTHUR   KINGSLEY    PORTER 


YALE  UNIVERSITY  PRESS 


UNIVERSITY  OF  CALIFORNIA 
AT  LOS  ANGELES 


THE  CONSTRUCTION  OF 

LOMBARD  AND  GOTHIC  VAULTS 


THE  CONSTRUCTION  OF 


LOMBARD  AND  GOTHIC  VAULTS 


BY 


ARTHUR  KINGSLEY  PORTER 


>,»)  >>»> 


'',  >».  >' 


NEW  HAVEN:  YALE  UNIVERSITY  PRESS 

LONDON:  HENRY  FROWDE 

OXFORD  UNIVERSITY  PRESS 

1911 


Copyright,  1911,  by 
Yale  University  Press 


Printed  from  type  November,  1911.      500  copies 


Art 
Library 

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THE  CONSTRUCTION  OF 

LOMBARD  AND  GOTHIC  VAULTS 


V 

^ 


160179 


THE    CONSTRUCTION    OF    LOMBARD 
AND    GOTHIC    VAULTS 

I 

THE  rib  vault  has  been  recognized  by  modern  archaeologists  as  the  cardinal 
and  essential  feature  of  Gothic  architecture,  the  motive  upon  the  develop- 
ment of  which  the  builders  of  the  XII  century  in  the  Ile-de-France  con- 
centrated their  energies,  and  from  which  followed  as  logical  and  almost  inevitable 
consequences  the  various  structural  and  ornamental  forms  characteristic  of  the 
Gothic  style.  Recent  historians  of  architecture  have  abandoned  the  methods 
of  the  old-school  archaeologists,  who  regarded  medieval  buildings,  without  con- 
sideration of  their  structural  significance,  as  so  much  ornament  to  be  analysed 
from  a  purely  aesthetic  viewpoint.  These  modern  writers  have  instead  studied 
in  the  greatest  detail  the  story  of  the  evolution  of  the  rib  vault  in  the  Ile- 
de-France,  the  many  experiments  essayed  in  its  applications,  and  the  various 
forms  it  assumed,  until  the  ultimate  Gothic  type  was  found.  They  have  demon- 
strated the  patience  and  perseverance  of  the  medieval  builders,  who  at  first  grop- 
ingly, later  more  confidently,  but  always  without  faltering,  surmounted  obstacle 
after  obstacle  until  they  had  created  a  new  and  pregnant  art.  The  result  of  these 
studies  has  been  to  emphasize  ever  more  strongly  the  importance  of  the  rib  vault 
as  the  generating  principle  of  Gothic  architecture. 

One  question,  however,  apparently  no  historian  of  architecture  has  yet  stopped 
to  ask  himself.  Granted  that  the  extraordinary  evolution  of  Gothic  architecture  i-— - 
was  due  primarily  to  the  rib  vault,  how  did  the  builders  of  the  transitional  period 
first  come  to  adopt  this  form.'*  Wliy  did  they  choose  it  in  preference  to  the  groin 
vault,  the  barrel  vault,  or  the  dome.''  The  earliest  examples  are  clumsy  and 
ponderous  constructions  possessing  over  other  types  of  vault  none  of  the  advan- 
tages structural  or  aesthetic,  of  which  the  form  later  proved  itself  capable.  It  is 
absurd  to  suppose  that  the  masons  were  gifted  with  prophetic  foresight,  and  con- 
sciously set  themselves  the  task  of  evolving  a  new  style  with  super-human  knowl- 
edge of  the  results  to  which  the  use  of  the  rib  vault  should  lead  them  a  century 
later.  The  explanation  must  be  that  the  rib  vault,  even  on  the  modest  scale  in 
which  it  was  first  employed,  possessed  certain  definite  advantages  that  were  lack-  V 
_i^ng  in  other  types  of  vault.     These  advantages  were  not  aesthetic,  since  the 

1 


2  THE   CONSTRUCTION  OF  LOMBARD  AND  GOTHIC   VAULTS 

earliest  rib  vaults  are  certainly  not  more  beautiful  than  contemporary  groin  or 
barrel  vaults.  They  were  not  structural,  that  is,  they  did  not  effect  the  ultimate 
stability  of  the  building,  the  concentration  and  counter-balancing  of  thrusts  and 
the  like,  for  the  earliest  rib  vaults  are  of  small  dimensions  and  placed  on  thick 
walls,  often  even  under  towers;  hence  any  other  form  of  vault  would  have  stood 
quite  as  well.  The  only  possible  explanation  is  that  rib  vaults  were  easier,  or  less 
expensive  than  others  to  build.  This,  in  fact,  was  the  case,  for  rib  vaults  may 
be  constructed  with  the  aid  of  a  very  light  centering  in  wood,  whereas  a  groin  or 
barrel  vault  requires  a  heavy  centering.  The  conclusion  therefore  seems  inevi- 
table that  the  desire  to  dispense  with  temporary  wooden  sub-structures  was  the 
sole  motive  which  induced  the  French  builders  to  adopt  the  rib  vault,  from 
the  logical  evolution  and  development  of  which  Gothic  architecture  came  into 
being. 

When  the  fact  that  rib  vaults  were  constructed  practically  without  centering 
is  born  in  mind,  it  is  easy  to  understand  many  heretofore  puzzling  features  of 
transitional  and  Gothic  architecture.  For  example,  doming  has  always  been 
recognized  as  an  essential  characteristic  of  Gothic  vaults.  Two  explanations 
have  been  offered  to  explain  this  doming:  one,  that  the  builders  were  not  suffi- 
ciently skilled  in  descriptive  geometry  to  be  able  to  bring  the  crowns  of  all  the 
arches  to  the  same  height;  the  other,  that  the  doming  had  the  purpose  of  con- 
centrating the  weight  and  thrust  of  the  vault  on  the  diagonals.  Neither  is  satis- 
factory. Since  the  builders  knew  enough  geometry  to  enable  them  to  bring  the 
crowns  of  the  arches  of  a  groin  vault  all  to  the  same  level,  they  could  certainly 
have  done  the  same  thing  with  the  rib  vault,  had  they  so  desired.  On  the  other 
hand,  as  I  have  already  said,  the  question  of  thrust  did  not  enter  into  these  early 
vaults.  The  true  explanfltinn  I  shall  show  to  be,  that  the  domed  form  facilitated 
construction  withouT^entering.  The  same  thing  may  be  said  of  various  other 
distortions  and  irregularities  of  early  vaults,  all  of  which  cease  to  be  enigmas  the 
moment  it  is  remembered  that  the  primary  aim  of  the  builders  was  to  dispense  as 
largely  as  possible  with  temporary  wooden  sub-structures.  Similarly,  it  becomes 
possible  to  understand  why  rib  vaults  were  in  early  times  placed  under  towers, 
even  in  churches  in  which  other  forms  of  vault  were  used  elsewhere.  Since  it 
was  awkward  to  erect  a  centering  between  four  solid  walls,  a  type  of  vault  which 
rniikLbp  erected-without  centering  was  preferred. 

Thus  a  knowledge  of  the  fact  that  it  was  a  fundamental  and  essential  prin- 
ciple with  the  Gothic  builders  to  erect  their  vaults  as  nearly  as  possible  without 
centering,  throws  a  new  light  upon  transitional  and  Gothic  architecture.  By 
aid  of  this  knowledge  it  becomes  possible  to  appreciate  the  daring  and  skill  of  the 
masons  who  learned  thus  to  build,  free-hand  as  it  were,  in  space;  it  becomes 
possible  to  understand  what  the  builders  were  striving  for  in  the  transitional 


¥ 


THE   CONSTRUCTION  OF  LOMBARD   AND   GOTHIC    VAULTS  3 

period,  and  to  grasp  the  purpose  of  the  many  different  experiments  they  tried 
in  the  construction  of  vaults. 

The  desire  to  economize  wood  k^d  to  the  introchiction  of  the  rib  vault,  not  only 
in  France,  but  in  Lombardy  as  well,  where,  indeed,  the  French  doubtless  learned  the 
construction.  The  Lombards  carried  the  principle  so  far  that,  in  certain  cases, 
wood  was  entirely  dispensed  with  in  the  edifice,  various  expedients  being  found  to 
erect  even  a  roof  without  it.  In  regions  where  wood  was  abundant,  however, 
vaults  were  erected  with  centering,  and  in  these  regions  the  rib  vault  was  never 
employed.  It  is  evident  that  the  Lombards  used  the  rib  vault  not  from  any  pref- 
erence for  the  form,  but  solely  because  it  could  be  constructed  without  centering. 

Rib  vaults  therefore  were  invented  in  Lombardy  as  a  simple  device  to  econo- 
mize wood.  They  were  adopted  by  the  French  builders  for  the  same  purpose. 
The  same  desire  to  dispense  with  temporary  wooden  substructures  governed  the 
development  of  architecture  during  the  entire  transitional  period,  and  eventually 
lead  to  the  birth  of  Gothic. 

If  space  permitted,  it  would  be  interesting  to  trace  across  the  centuries  the 
chronological  development  and  growth  of  this  principle.  I  shall,  however,  con- 
fine myself  to  a  demonstration  of  the  fact  that  the  principle  existed,  beginning 
with  a  brief  summary  of  certain  known  methods  of  vault  construction  used  by  the 
Roman  and  Byzantine  builders,  since  these  are  analogous  to,  and  partly  explain, 
medieval  constructions.  I  shall  then  take  up  the  rib  vaults  of  France,  of  which 
the  study  offers  less  difficulty  since  there  is  extant  an  abundant  series  of  well 
preserved  monuments.  The  French  principles  of  construction  once  understood, 
it  will  not  be  difficult  to  see  that  the  Lombard  methods  were  parallel  and  similar, 
but  not  identical.  Without  knowledge  of  the  methods  employed  in  France,  it 
would  be  difficult  to  discover  the  Lombard  methods,  owing  to  the  fact  that  com- 
paratively few  examples  of  Lombard  vaulted  constructions  have  escaped  the 
vandalism  of  the  barocco  centuries  and  the  equally  deplorable  barbarism  of 
restorations  executed  during  the  last  forty  years  —  restorations  which  have 
almost  invariably  destroyed  what  they  pretended  to  preserve.  Moreover  these 
few  examples  are,  in  the  great  majority  of  cases,  covered  with  plaster  and  intonaco, 
so  that  a  study  of  the  masonry  is  impossible.  It  is  necessary  therefore  to  leave 
the  study  of  Lombard  vaults  for  the  last,  even  at  the  expense  of  violating  strict 
historical  sequence. 

II 

Choisy  '  has^hown  that  in  the  construction  oftheir  vaults  the  Romans  sought 
primarily  to  avoid  expensive  temporary  centering  in  wood.^     A  light  skeleton  of 

'  Auguste  Choisy,  L'art  de  haiir  chez  les  Romains.     Paris,  Duchcr  &  Cie.,  1873.     Folio. 

'  The  very  futihty  of  the  objections  urged  against  his  conclusions  in  this  particular  by  certain  English 


0 


4     THE  CONSTRUCTION  OF  LOMBARD  AND  GOTHIC  VAULTS 

timber  was  erected,  a  mere  mould,  of  the  shape  and  form  of  the  vault  to  be  built. 
On  this  mould  was  placed  a  sort  of  permanent  centering  of  light  bricks  or  tiles, 
not  heavy  enough  to  crush  the  mould,  but  strong  enough  when  finished  to  act  as 
a  centering  for  the  massive'  of  the  vault  (which  consisted  of  a  rubble  concrete) 
and  to  prevent  any  deformation  or  rupture  of  the  wooden  mould.  (Figs.  1  and  2.) 
This  permanent  centering  was  formed  in  various  ways,  always,  however,  with 
the  same  end  in  view.  Sometimes  broad  flat  tiles  were  laid  in  one  or  two  layers 
broad-side  on  the  mould,  making  a  complete  and  self-supporting  arch  above  it, 
the  joints  of  the  tiles  being  covered  with  other  smaller  tiles,  and  certain  ones  being 
placed  vertically  to  give  a  key  for  the  superimposed  concrete  (Fig.  1).  At  other 
times  the  bricks  were  placed  so  as  to  form  a  continuous  open-work  skeleton  in 
whose  rectangular  or  rather  wedge-shaped  interstices  was  placed  the  cement 
rubble  forming  the  massive.  Again,  the  bricks  of  the  permanent  centering  were 
disposed  to  form  ribs  or  chains  crossing  the  vault  at  convenient  intervals.  This 
last  was  the  system  commonly  employed  in  connection  with  groin  vaults  (Fig.  2). 
The  chains  were  often  composed  of  bricks  so  laid  as  to  afford  an  irregular  out- 
line with  their  protruding  or  receding  members  which  formed  a  key  for  the 
rubble  massive,  always  applied  in  horizontal  courses  or  layers;  they  followed  the 
lines  of  the  groins  and  sometimes  also  those  of  the  longitudinal  and  transverse 
arches.  Sometimes  the  two  methods,  that  of  flat  tiles  and  that  of  interior  chains, 
were  used  simultaneously.  But  in  all  cases  the  purpose  was  the  same  —  i.e.,  to 
afford  a  permanent  centering  in  brick,  which,  placed  on  top  of  a  light  wooden 
mould,  might  enable  the  builders  to  construct  the  vault  without  other  temporary 
wooden  centering  than  the  mould  itself.  Once  finished,  the  vault  became  a  solid 
concrete  mass  to  which  the  chains  or  ribs  adhered  as  an  integral  part,  but  in  which 
they  performed  iio  strengthening  nor  structural  function.  It  is  well  to  insist  on 
this  fundamental  and  essential  fact,  for  a  recent  writer  of  authority  has  pub- 
lished a  groin  vault  in  the  familiar  ruin  of  the  Roman  Campagna  known  as  "Sette 
Basi"  (Fig.  2),  as  having  projecting  ribs.  Such  a  construction  would  be  entirely 
foreign  to  the  spirit  of  the  Roman  art  of  building.  To  erect  a  vault  of  this  kind 
with  salient  ribs  would  require  a  most  elaborate  and  uselessly  complicated  cen- 
tering, since  grooves  would  have  to  be  made  in  it  for  the  ribs.  Moreover,  the  ribs 
would  not  then  perform  nearly  so  well  their  only  structural  function,  that  of  act- 
ing as  a  centering,  since  their  projection  would  prevent  their  being  properly  keyed 
into  the  vaults.  At  present,  as  may  be  seen  in  the  photograph  (Fig.  2)  the  ribs 
of  this  vault  actually  do  project  slightly  from  the  surface.     The  vault  having  been 

writers  is,  perhaps,  the  most  convincing  argument  for  the  general  soundness  of  his  deductions,  as,  I  think, 
any  impartial  archaeologist  who  has  examined  on  the  spot,  Choisy's  book  in  hand,  the  ruins  of  Rome  and  the 
Campagna  will  be  forced  to  admit. 

'  I  employ  this  word  to  denote  the  body  or  core  of  the  vault  as  distinct  from  the  ribs. 


Fig.   1.      Vault  in  Ruin  known  as  "Roma  Vecchia",  near  Via  Appia 
about  7  kilometers  from  Rome. 


Fig.    3.      .\mphithcater,  Champlieu,  (Oise). 


Fig.   2.      Ancient  ruin,  known  as  "Sette  Bast",  Via  Tuscolana,  about 
7j  kilometers  from  Rome. 


THE  CONSTRUCTION  OF  LOMBARD  AND  GOTHIC  VAULTS  5 

exposed  for  centuries  to  the  corrosion  of  water  and  the  atmosphere  has  weathered 
irregularly;  consequently  the  massive,  consisting  of  more  perishable  materials, 
has  chipped  oft"  and  disappeared  faster  than  the  bricks.  The  same  uneven 
weathering  may  be  observed  in  the  vaults  of  the  Thermae  of  Diocletian,  and  in 
the  ruins  of  the  Palatine. 

Vaults  constructed  on  the  Roman  principle  should,  theoretically,  exercise  but 
Uttle  thrust,  being  when  finished  a  solid  mass  of  concrete.  As  a  matter  of  fact, 
however,  the  elasticity  of  the  concrete  causes  them  to  exercise  considerable  out- 
ward pressure,  which,  as  the  Romans  perfectly  understood,  required  buttressing. 
Notwithstanding  the  fact  that  Roman  walls  were  commonly  of  such  enormous 
thickness  as  to  be  able  to  bear  these  thrusts  without  need  of  external  re-enforce- 
ment, the  architects  nevertheless  contrived  their  plans  with  great  ingenuity  so 
that  the  thrust  of  one  vault  should  be  neutralized  by  that  of  another,  or  so  that 
an  interior  spur  wall  strengthened  the  exterior  wall  at  the  critical  points.  Exterior 
salient  buttresses  seem  to  have  been  avoided,  probably  for  aesthetic  reasons. 
That  the  Romans  were  fully  aware  of  the  possibility  of  their  use,  however,  and 
employed  them  when  it  was  not  possible  to  place  the  buttress  internally,  is  proved 
by  the  fact  that  such  buttresses  were  actually  used  to  re-enforce  a  sort  of  apse  in 
the  "Sette  Basi"  and  also  to  strengthen  the  exterior  wall  of  the  Amphitheatre  of 
Champheu,  Oise  (Fig.  3),  and  in  other  instances  as  well.  The  buttresses  of 
Champlieu  were  perhaps  added  to  the  original  construction,  but  still  in  the  Roman 
period  (not  in  the  Merovingian,  as  has  been  stated),  a  fact  proved  by  the  charac- 
ter of  the  masonry.  They  are  especially  significant,  for  the  wall  being  merely  a 
retaining  wall  for  the  solid  mass  on  which  was  supported  the  cavea,  an  interior 
buttress  became  an  impossibility.  Thus  it  is  evident  that  the  Romans  were  per- 
fectly acquainted  with  the  possibilities  of  external  buttressing,  and  employed  it 
when  necessary,  although  they  preferred  internal  buttressing.  The  buttresses  of 
Champlieu  even  end  in  a  sloping  glacis,  a  feature  which  has  heretofore  been  con- 
sidered exclusively  Gothic.  I  insist  upon  these  buttresses  of  Champlieu  because 
they  prove  that  external  buttressing  of  vaults,  a  system  which  has  been  con- 
sidered purely  medieval,  was  in  fact,  like  many  another  detail  of  vault  construc- 
tion, merely  a  survival  of  Roman  tradition. 

Roman  vaults  with  brick  chains  and  ribs  were  of  course  in  general  erected 
not  throughout  the  empire  but  only  where  suitable  materials  could  be  found,  i.e., 
in  Rome  itself  and  its  environs,  although  the  system  was  more  extended  than 
usually  supposed,  since  a  half-dome  with  brick  ribs  is  found  in  the  so-called 
Palace  of  Constantine  at  Aries.  In  the  provinces  the  vaults  were  in  general 
constructed  of  ashlar  masonry,  to  erect  which  a  full  centering  was  very  frequently 
employed;  but  in  the  Amphitheatre  and  so-called  Temple  of  Diana  at  Nimes, 
in  the  Pont-du-Gard,  and  in  a  host  of  monuments  of  Syria  and  Africa,  various 


L^ 


THE   CONSTRUCTION  OF  LOMBARD  AND   GOTHIC   VAULTS 


ingenious  devices  to  economize  centering,  even  in  such  vaults,  were  used.  These 
various  expedients,  although  highly  interesting  and  instructive  in  themselves,  need 
not  be  described  here,  since  they  have  already  been  admirably  studied  by  Choisy 
and  do  not  concern  the  subject  under  examination  except  in  so  far  that  they  all 
demonstrate  the  striving  of  the  Roman  architects  to  build  vaults  with  a  minimum 
of  temporary  wooden  centering. 
N55J^  The  Byzantine  builders,  in  the  construction  of  their  vaults,  as  in  so  much  else, 
merely  developed  and  extended  Roman  principles.'  With  true  Greek  subtlety  of 
intellect  they  grappled  with  the  problem  of  discovering  means  to  erect  vaults 
without  centering,  and  hit  upon  a  vast  number  of  clever  and  ingenious  devices  to 
compass  this  end.  The  subject  became  a  passion  with  them,  and  governed  the 
whole  development  of  their  architecture,  even  more  than  it  had  that  of  Roman 
architecture.  Of  all  the  many  expedients  they  found  by  which  either  to  dispense 
with  entirely,  or  to  reduce  to  a  minimum,  the  use  of  centering  in  the  construction 
of  vaults,  only  one  seems  to  have  influenced  medieval  architecture  in  the  Occident. 
That  was  the  device  of  giving  the  groined  vault  a  domical  form  (Fig.  4).     A  vault 

of  this  shape  could  be,  and  was,  erected  by  the  aid  of  six 
light  wooden  arches,  two  following  the  lines  of  the  groins, 
now  made  semi-circular  and  no  longer  elliptical,  and  the 
four  others  following  the  walls  and  transverse  arches.  The 
vaults  being  constructed  of  brick,  the  courses  marked  1  in 
our  diagram  (Fig.  4)^  could  be  laid,  the  adhesion  of  the 
mortar  sufficing  to  keep  the  bricks  in  place.  Then  could 
be  placed  the  courses  2  and  then  those  3  and  so  on,  the 
inclined  surfaces  of  the  vault  giving  each  brick  a  point  of 
partial  support  on  the  brick  below  it  in  the  same  course 
and  against  the  bricks  of  the  preceding  course,  so  that  the 
adhesion  of  the  mortar  sufficed  to  hold  it  in  position.  Owing 
to  the  domed  shape  of  the  vault,  each  course  assumed  the 
form  of  a  segment  of  a  circle,  and  thus,  when  completed, 
became  a  sort  of  arch  which  was  self-supporting.  Only  for 
the  middle  courses  5  was  the  help  of  a  cerce  perhaps  neces- 
sary. In  the  construction  of  vaults  of  this  character,  the 
Byzantine  architects  found  it  useful  to  employ  for  the  wall  arches  a  salient  wall 
rib  in  masonry,  instead  of  a  centering  in  wood.  This  could  be  constructed  with- 
out centering  by  the  well  known  Byzantine  method.  Salient  ribs  in  masonry 
were  substituted  also  for  the  centering  following  the  line  of  the  transverse  arches. 

'  Auguste  Choisy,  L'art  dc  bdlir  chez  les  Byzantins.     Paris,  Societe  Anonyme  de  Publications  Periodiques, 
1883.     Folio. 

'  For  the  sake  of  clearness  the  width  of  the  courses  has  of  course  been  much  exaggerated  in  this  diagram . 


»V»-      3  4-  5  *  J       V 

t.\  /t. 

/^X.\   J     I    <■     I     J     I     t    I    >    |l^ 


Fig.  4 


THE  CONSTRUCTION  OF  LOMBARD   AND   GOTHIC  VAULTS  7 

A  firm  permanent  centering  in  masonry  was  desirable  at  this  point  not  only  to  aid 
in  the  constrnetion  but  to  conceal  and  strengthen  any  imperfections  in  the  con- 
junction of  the  masonry  of  two  adjoining  vaults,  and  to  guard  this  critical  point 
against  any  possible  deformation.  Moreover,  the  use  of  these  transverse  ribs 
made  it  possible  to  erect  one  vault  (juite  independently  of  the  neighboring  one. 
Byzantine  groin  vaults  of  the  domed  type  were  introduced  into  Italy  at  an  early 
epoch,  and  several  are  still  perfectly  i)rcserved  at  S.  Vitale  of  Havenna.  It  is 
probable  that  they  were  also  erected  elsewhere  in  the  peninsula,  for  Byzantine 
influence  during  the  V  and  VI  centuries  was  by  no  means  limited  to  the  shores 
of  the  Adriatic  —  witness  the  chapel  of  S.  Satiro  at  S.  Ambrogio  of  Milan, 
S.  Lorenzo  in  the  same  city,  and  the  baptistry  of  the  Cathedral  of  Naples. 

In  the  East  the  Byzantine  builders  learned  how  to  dispense  entirely  with  the 
use  of  centering  in  the  erection  of  groin  vaults,  disposing  tiie  stone  courses  after 
the  manner  of  a  dome,  as  in  Figs.  5  and  G.     (Iroin  vaults  of  the  type  of  P'ig.  .5  I 


D 

Fig.  5 


Fig.  6 


have  never  observed  in  the  West;   vaults  of  the  type  of  Fig.  G,  however,  are  found 
in  the  Porta  Ticinese  of  Milan  and  at  Santa  ISIaria  Maggiore  of  Lomello.' 

Such  in  outline  were  those  Roman  and  Byzantine  methods  of  construction, 
which  offer  some  analogy  to  the  methods  of  the  medieval  builders.  In  construc- 
tion as  in  ornament  ancient  traditions  never  died.  Under  the  hands  of  medieval 
architects,  building  methods  underwent  transformations  and  clianges,  assumed 
new  forms  and  developments,  but  they  always  retained  something  of  their  original 
classical  form.^^  This  was  due  not  only  to  the  existence  of  a  continuous  tradition 
but  also  to  the  fact  that  Roman  ruins  existed  well  nigh  throughout  Europe,  ever 
present  as  object  lessons  to  the  masons.  Thus  it  happened  that  just  as  the  Corin- 
thian capital  survived  throughout  the  INIiddle  Ages,  .sometimes  almost  in  its  origi- 
nal form,  at  others  developed  or  simplified,  .so  Roman  and  Byzantine  principles 
of  construction  were  the  basis  from  which  were  developed  all  meilieval  achieve- 
ments in  the  art  of  building.  'I 


l^ 


'  These  vaults  I  have  published  in  Arte  e  Storia,  Anno  xxx,  1!)1 1,  ji.  19(i. 


THE   CONSTRUCTION  OF  LOMBARD   AND   GOTHIC   VAULTS 


III 

When  these  Roman  and  Byzantine  methods  of  construction,  so  admirably 
demonstrated  by  Choisy,  are  borne  in  mind,  it  is  not  difficult  to  discover  the 
method  of  construction  employed  in  a  Gothic  rib  vault.  Indeed,  Viollet-le-Duc  ' 
and  Choisy  -  have  both  recognized  that  Gothic  vaults  were  erected  practically 
without  the  use  of  other  centering  than  a  light  frame  for  the  ribs  and  a  cerce  for  the 
the  upper  courses.  Neither  of  these  writers,  however,  appears  to  have  realized 
the  significance  of  the  fact. 

It  is  obvious,  and  I  think  has  so  been  recognized  by  every  writer  on  the  sub- 
ject, that  the  ribs  of  a  rib  vault  were  erected  first.  They  were  always  self-sup- 
porting arches,  even  when  broken  or  curved  in  plan.  The  proof  of  this  statement 
is  that  in  many  ruined  abbeys,  such  as  that  of  Ourscamps,  for  example,  the  ribs 
still  stand  intact,  although  the  massive  of  the  vault  has  fallen;  and  these  ribs 
still  stand  not  only  in  the  bays  where  the  vaulting  was  rectangular,  but  in  the 
ambulatory  where  the  compartments  are  of  irregular  shape  and  the  ribs  broken 
in  plan.  Since  these  broken  ribs  are  self-supporting  now  that  the  massive  has 
disappeared,  they  must  have  been  equally  self-supporting  before  it  was  built. 

A  very  light  centering  would  suffice  to  erect  the  ribs.  Especially  if  the  arches 
were  pointed,  the  voussoirs  of  the  lower  part  of  the  arch  would  be  self-support- 
ing, and  the  lightest  kind  of  a  frame  would  enable  the  builders  to  slip  in  the  upper 
voussoirs  forming  the  key. 

When  the  ribs  had  been  erected,  the  massive  of  the  vault  could  be  constructed 
for  a  certain  distance,  about  one  third  of  its  height,  without  any  centering  at  all. 
The  remainder  of  the  courses  were  erected  by  the  use  of  a  simple  movable 
cerce  (Fig.  7)  hung  on  the  ribs  and  moved  to  the  next 
course  after  each  in  turn  had  been  completed,  each  course 
when  finished  being  arched  and  self-supporting  on  the  prin- 
ciple already  explained  (Fig.  4).     That  is  why  Gothic  vaults 
always  preserved  something  of  the  domical  form  —  a  simple  fact  for  which  so 
many  far-fetched  explanations  have  been  offered.' 

'  Dictionnaire  raisonne  de  V architecture  frangoMe  du  XI  au  XVI  Steele.  Paris,  Bauce,  1854-68.  11  vols. 
Especially  article  on  Construction. 

2  Histoire  de  V architecture.     Paris,  Gauthier-Villars,  1899.  2  vols.  8vo. 

•  In  this  connection  it  is  interesting  to  cite  a  passage  of  Suger  {De  Consecratione,  ed.  A.  Lecoy  de  la  Marche, 
(Euvres  completes  de  Suger.  Paris,  Renouard,  1867.  8vo.,  p.  230)  which  gives  documentary  confirmation  of 
what  has  been  said  above  in  regard  to  the  construction  of  Gothic  vaults: 

Nee  illud  etiam  silere  dignum  duximus,  quod  dum  prsefatum  novi  augmenti  opus  capitellis  et  arcubus 
superioribus  et  ad  altitudinis  cacumen  produceretur,  cum  necdum  prinnpales  arcus  singulariter  veluti  voltarum 
cumulo  cohcererent,  terribilis  et  pene  tolerabilis  obnubilatione  nubium,  inundatione  imbrium,  impetu  validissimo 
ventorum  subito  tempestatis  exorta  est  procella;   quae  usque  adeo  invaluit,  ut  non  solum  validas  domos,  sed 


THE   CONSTRUCTION  OF  LOMBARD   AND   GOTHIC   VAULTS 


IV 

Such  was  the  theory  of  Gothic  rib  vault  construction.  The  workings  of  the 
system  in  actual  practice  will  be  evident  upon  examination  of  some  of  the  pecu- 
liarities of  extant  French  vaults  of  the  Gothic  and  transitional  periods. 

In  large  vaults  over  naves  in  the  Ile-de-France,  as  far  as  my  observation  goes, 
there  is  usually  a  sharp  break  in  the  character  of  the  masonry  at  the  point  where 
it  became  necessary  to  employ  a  cerce  (Fig.  10).  Below  this  point,  large  stones 
are  used;  above,  so  as  not  to  overcharge  the  light  centering,  the  courses  are  nar- 
row and  light,  although  sometimes  the  stones  resting  on  the  wall  rib  and  hence 
supported  by  it  in  large  part  are  heavier  (Left  hand  bay.  Fig.  9).  In  such  vaults 
the  history  of  the  construction  is  written  almost  as  plainly  as  if  the  cerce  had 
been  left  in  position. 

Similarly  it  happens  very  frequently,  in  fact  it  is  not  too  strong  to  say  gener- 


cby 


Fig.  8 

ally,  in  Gothic  vaults,  that  the  courses,  instead  of  being  normal  to  the  walls,  tend 
to  converge  towards  the  central  key-stone,  as  in  Fig.  8.  The  purpose  evidently 
was  to  incline  the  courses  more,  and  to  give  each  stone  a  firmer  point  of  support 
on  the  stone  placed  below  it,  thus  relieving  the  cerce  of  a  corresponding  amount 
of  weight.  Gothic  builders  were  not  only  logical,  but  as  subtle  and  ingenious  as 
the  Byzantine  architects. 

etiam  lapideas  turres  et  ligneas  tristegas  concusserit.  Ea  tempestate,  quadam  die,  anniversario  gloriosi  Dago- 
berti  regis,  cum  venerabilis  Carnotensis  episcopus  Gaufredus  missas  gratiarum  pro  anima  ejusdem  in  conventu 
ad  altare  principale  festive  celebraret,  tantus  oppositorum  ventorum  impetus  prtefatos  arcus  nulla  suffultos 
podio,  nullis  renitentes  suffragiu  impingebat,  ut  miserabiliter  tremuli,  et  quasi  hinc  et  inde  fluctuantes  subito 
pestiferam  minarentur  ruinam.  Quorum  quidem  operturarumque  impulsionem  cum  episcopus  expavesceret, 
saepe  manum  benedictionis  in  ea  parte  extendebat,  et  brachium  sancti  senis  Simeonis  signando  instanter  op- 
ponebat,  ut  manifeste  nulla  sut  constantia,  sed  sola  Dei  pietate  et  Sanctorum  merito  ruinam  evadere  appare- 
ret.  Sicque  cum  multis  in  locis  firmissimis,  ut  putabatur,  aedificiis  multa  ruinarum  incommoda  intulisset, 
virtute  repulsa  divina,  titubantibus  in  alto  solis  et  reeentibus  arcubus,  nihil  proferre  prsevaluit  incommodi. 


10  THE   CONSTRUCTION   OF    LOMBARD  AND   GOTHIC  VAULTS 

111  the  vaults  the  stone  courses  are  seldom  perfectly  regular.  It  is,  indeed,  not 
rare  to  find  them  as  irregularly  disposed  as  in  Fig.  9,  one  stone  being  cut  to  fill  an 
odd-shaped  opening  between  two  others,  courses  twisting  and  dying  away,  at 
times  frankly  broken.  Obviously  the  stones  of  such  vaults  were  never,  as  has 
been  too  often  repeated,  cut  in  the  quarry  to  fit  their  final  position.  The  convex 
and  ungeometrical  forms  the  stones  assume  in  this  irregular  masonry  prove  that 
a  mason  has  taken  the  stones,  squared  at  the  quarry  without  any  idea  of  adapt- 
ing them  to  a  particular  place,  and  has  cut  them  down  to  occupy  their  present 
position.  Even  ribs  were  only  roughly  blocked  out  before  being  put  in  place, 
and  the  mouldings  were  carved  afterwards.  This  is  proved  by  the  fact  that^at 
Foulanques  (Oise),  Cambronne  (Oise),  Bethisy-St.-Pierre  (Oise)  (Fig.-  11)  and 
elsewhere,  the  roughly  blocked  out  ribs  still  exist,  the  mouldings  never  having 
been  executed. 

In  many  transitional  vaults,  such  as  the  one  of  Crezancy  (Aisne)  of  which  I 
give  a  photograph  (Fig.  1''2),  one  rib  is  perfectly  straight,  the  other  is  bent.  Un- 
fortunately in  the  case  here  illustrated  the  vault  has  been  smeared  with  plaster 
and  this  painted  with  imitation  stone  joints  which  belie  the  real  ones.  It  is  easy 
to  see,  however,  that  the  straight  arch  was  constructed  first,  and  that  its  keystone 
had  an  amortisement  to  which  the  second  diagonal  was  to  be  attached.  But  the 
unskillful  builders  placed  this  amortisement  not  quite  true,  not  precisely  in  the 
direction  of  the  springing  of  the  second  diagonal.  Therefore  to  join  the  diagonal 
to  the  amortisement,  it  was  necessary  to  twist  the  former. 

The  entire  transitional  period  resolves  itself  into  a  series  of  experiments  on 
the  part  of  the  builders  to  erect  vaults  with  a  minimum  of  centering.  The  dis- 
like of  wasting  energy  on  a  purely  temporary  structure  was  probably  the  reason 
they  wished  to  dispense  with  centering,  for  I  do  not  believe  that  there  was  any 
actual  scarcity  of  wood,  a  material  fairly  abundant  in  Northern  France,  and 
never  stinted  in  constructing  the  roofs  of  the  great  cathedrals,  often  a  veritable 
forest  of  timbers.' 

'  Yet  that  it  was  at  times  hard  to  find  is  proved  by  a  passage  of  Suger:  Cumque  pro  trabium  inventione 
tam  nostros  quam  Parisienses  lignonim  artifices  consuluissemus,  responsiim  nobis  e>^t  pro  eorum  existiniatione 
verum,  in  finibus  istis  propter  silvarum  inopiam  minime  inveniri  posse,  vel  ab  Autissiodorensi  pago  necessario 
devehi  oportere.  Cumque  omnes  in  hoc  ipso  consonarent,  nosque  super  hoc  tam  pro  laboris  magnitudine 
quam  pro  operis  longa  delatione  gravaremur,  nocte  quadam,  a  matutinarum  obsequio  regressus,  lecto  cogitare 
coepi  meipsum  per  omnes  partium  istarum  silvas  debere  procederc,  circumquaque  perhistrare,  moras  istas  et 
labores,  si  hie  inveniri  possent,  alleviare.  Moxque  rejectis  curis  aliis,  summo  mane  arripiens,  cum  carpen- 
tariis  et  trabium  mensuris  ad  silvam  quae  dicitur  Ivilina  acceleravimus.  Cumque  per  terram  nostram  Cap- 
reolensis  valHs  transiremus,  accitis  servientilnis  nostris  nostrarum  custodibus  et  aharum  silvarum  peritis, 
adjurando  fide  et  sacramento  eos  consuluimus,  si  ejus  mensurae  ibidem  trabes  invenire  quocumque  labore 
veleremus.  Qui  subridens,  si  auderent,  potius  deriderent;  admirantes  si  nos  plane  nesciremus  in  tota  terra 
nihil  tale  inveniri  posse,  maxime  cum  Milo  Capreolensis  castellanus  homo  noster,  qui  medietatem  silvae  a 
nobis  cum  alio  feodo  habet,  cum  sustinuisset  tam  a  domino  rege  quam  ab  Amalrico  de  Monte  Forti  longo 


Fig.   9.      St.-Leger,  Soissons,  (Aisne). 
Vaults  of  Choir. 


Fig.    10.      Cathedrale,  Soissons,    (Aisne). 
Navi'  Vaults. 


^ 

V 

-■ 

^w 

,  Ji 

Hr 

,. 

F^ 

)£'^ 

-n^ 

r<<j 

r-H- 

T-S 

,  •/)   II    ' 

v/^ 

1     1 

T         ' 

.^  1  .  1 

/III 

}LL.      1         1 

tr-V 

M' 

- 

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(  1   I    t  ^   1    I   1 


Fig.    11.      St. -Pierre,    Bethisy  -  St.  -  Kerre,  (Oi.se). 
South  side  aisle. 


Fig.   12.     Notre  -  Dame,  Crezancy,  (Aisne). 
Vault  of  Crossing. 


Fio.    13.      Crouy-sur-Ourcq,   (Seine-et-Oise). 
Vault  under  Tower. 


Fig.    U.      St.  -  Pierre,  Ary-en-Mullien,  (Oise). 
\'ault  beneath  Tower. 


Fi<;.   \ii.     Sts.  -  Gervais-et-Protais,  Rhuis,  (Oise). 
South  side  aisle,  Vault  of  ea.stem  Chapel. 


Fig.    10.     Sts.  -  Gervai.s-et-Protais.  Rhuis,  (Oise). 
North  side  aisle.  Vault  of  eastern  Chapel. 


THE  CONSTRUCTION  OF  LOMBARD  AND  GOTHIC   VAULTS  11 

But  though  wood  was  available,  it  was  costly  to  work;  the  practical  spirit  of 
the  French  masons  caused  them  to  seek  means  to  erect  vaults  not  only  as  well, 
but  as  simply  and  as  economically  as  possible.  Hence  they  had  recourse  to  the 
rib  vault. 

In  the  earliest  examples  of  rib  vaults  in  the  Ile-de-France,  such  as  those  in  the 
churches  of  Crouy-sur-Ourcq,  Seine-et-Oise  (Fig.  13)  or  Acy-en-Multien,  Oise 
(Fig.  14),  the  advantages  of  doming  and  of  wall  ribs  were  not  yet  appreciated. 
The  diagonals  were  made  needlessly  heavy  and  must  have  reciuired  a  very  clumsy 
centering.  But  in  the  rib  vault  of  Rhuis,  Oise  (Fig.  15),  which  according  to  Mr. 
Lefevre-Portalis'  is  the  oldest  of  the  Soissonnais,  the  ribs  are  already  lighter, 
and  there  is  a  slight  but  perceptible  doming.-  This  vault  was  not  erected  with  a 
solid  centering.  It  is  sufficient  to  compare  it  with  the  groin  vault  in  the  sym- 
metrical position  in  the  north  aisle  (Fig.  16),  which  was  erected  with  centering 
and  which  is  not  domed,  to  be  convinced  of  the  fact.  It  is  equally  certain  that 
the  vaults  of  Acy-en-Multien  and  Crouy-sur-Ourcq  though  not  domed  were  also 
built  without  solid  centering,  as  was  perfectly  possible  in  vaults  of  such  restrained 
dimensions.  In  fact,  long  after  the  advantages  of  doming  were  thoroughly  under- 
stood, the  transitional  builders  reduced  it  to  a  minimum  or  dispensed  with  it 
altogether  in  certain  vaults  of  small  size,  as,  for  example,  those  of  the  ambulatory 
of  Morienval,  since  such  were  easily  built  without  this  aid,  even  when  no  center- 
ing was  used.  It  is  a  safe  assertion  that  all  domed  or  ribbed  vaults  of  the  XII 
century  were  constructed  without  solid  centering.  If  the  reader  doubts,  let  him 
imagine  the  difficulty  of  grooving  a  wooden  centering  around  the  ribs,  or  mould- 
ing its  surface  to  the  complex  double  curvature  of  a  domical  vault.  The  early  rib 
vaults  of  the  Ile-de-France  were  introduced  in  side  aisles  or  under  towers,  and 
were  of  small  dimensions.  The  builders  had  long  been  accustomed  to  build  in 
these  positions  groin  vaults  of  whose  stability  there  was  nothing  to  be  feared.  If 
they  abandoned  groin  vaults  for  rib  vaults,  it  was  because  they  wished  to  dis- 
pense with  solid  centering. 

tempore  guerras,  ad  tristegas  et  propugnacula  facienda  nihil  tale  iilibatum  vel  intactum  prffteriisset.  Nos 
autem  quicquid  dicebant  respuentes,  quadani  fidei  nostrae  audacia  silvam  perlustrare  ca^piimis,  et  versus 
quidem  primani  horain  trabeni  unam  mensurse  sufficientem  invenimus.  Quid  ultra?  usque  ad  nonam  aut 
citius  per  fruteta,  per  opacitatem  silvarum,  per  densitatera  spinarum,  duodecim  trabes  (tot  euim  necessarioe 
erant)  in  admirationem  omnium  proesertim  circumstantium  assignavimus,  et  ad  basilicani  sanetam  deportatas 
cum  exultatione  novi  operis  operturae  superponi  fecimus,  ad  laudem  et  gloriam  Domini  Jesu,  qui  sibi  sanetisque 
Martyribus,  a  manibus  raptorum  protegens,  sicut  facere  voluit,  reservaverat.  Nee  igitur  superflua,  nccque 
minus  eontinens  id  ciroa  divina  extitit  largitio,  qua;  in  pondere  et  mensura  omnia  moderari,  omnia  dare  con- 
stituit,  cum  ultra  quam  oportuit  nulla  ulterius  inveniri  potuerit.  —  Sugerii,  De  Consecratiotie,  ed.  A.  Lecoy  de 
la  Marche,  (Euvres  completes  de  Suger,  Paris,  Renouard,  1867.  8vo.,  p.p.  221-222. 

'  Architecture  religieuse  dans  I'ancien  diocese  de  SoissoTis.  Paris,  Plon  Nourrit  &  Cie.,  1894.  Folio.  \'ol.  II, 
p.  222. 

'  This  fact,  which  has  been  denied,  I  have  tested  by  measures  on  the  spot. 


12  THE    CONSTRUCTION  OF  LOMBARD  AND  GOTHIC  VAULTS 

The  rib  vault  of  the  porch  at  Moissac,  Tarne-et-Garonne  (Fig.  18),  was  pecu- 
Harly  constructed.  The  diagonals,  .70  meters  broad,  are  composed,  not  of  a 
single  set  of  voussoirs,  but  of  jointed  masonry.  The  stereotomy  of  this  masonry 
at  the  intersection  makes  it  evident  that  both  diagonals  were  erected  at  the  same 

time,  not  one  before  the  other  as  was  usual  (Fig.  17).     The 
^"^^  vault  has  heavy  wall  ribs  in  two  orders,  but  is  not  domed. 

The  builders  have,  however,  found  a  substitute  for  doming 
in  a  new  expedient.  The  diagonals  are  heavily  loaded 
with  a  new  set  of  voussoirs  at  their  haunches;  this  super- 
imposed masonry  dies  away  toward  the  crown  and  the 
springing.  ^Yhile  undoubtedly  intended  in  part  as  a  but- 
tress to  protect  the  vault  against  any  possible  upward 
rupture  caused  by  the  not  inconsiderable  thrust  of  these 
clumsy  diagonals,  this  loading  had  another  purpose  as 
well.  It  considerably  increased  the  curve  of  the  vault  sur- 
face and  hence  facilitated  construction  without  centering. 

The  rib  vault  of  Ste. -Croix  at  Quimperle,  Finistere,  (Fig.  22),  was  similar  in 
type  (at  least  as  far  as  it  is  possible  to  judge  from  the  modern  copy,  which  is  all 
we  have  left  to  study  it  by),  except  that  the  diagonals  were  not  loaded.  This 
vault  is  notable  because  of  its  considerable  size  (7.36  x  6.46  meters),  and  the 
height  at  which  it  was  erected.  Groin  or  barrel  vaults  were  used  elsewhere  in 
the  church,  and  I  was  long  puzzled  as  to  why  a  rib  vault  should  have  been  chosen 
only  for  the  cupola.  The  fact,  however,  has  a  perfectly  simple  explanation. 
This  cupola  was  originally  surmounted  by  a  tower.  It  would  have  been  exceed- 
ingly difficult  to  erect  a  vault  on  a  solid  centering  in  such  a  position.  Not  only 
would  much  labor  have  been  wasted  in  transporting  the  material  to  be  used, 
since  this  would  have  had  to  be  first  raised  to  the  roof,  then  transferred  to  the 
top  of  the  tower  walls,  and  finally  lowered  again  to  the  vault  where  it  was  to  be 
employed  —  but  it  would  also  have  been  a  very  delicate  task  to  shape  from  above 
a  wooden  centering  to  the  form  desired.  In  a  rib  vault,  however,  these  difficulties 
could  be  avoided,  since  the  absence  of  solid  centering  made  it  possible  to  pre- 
serve an  opening  of  communication  between  the  extrados  and  the  floor  below 
until  the  very  moment  of  the  completion  of  the  vault.  The  masons  could  hence 
work  from  below  instead  of  from  above.  For  this  reason  rib  vaults  were  pre- 
ferred to  other  forms  under  towers,  not  only  at  Quimperle,  but  in  many  transi- 
tional edifices  of  the  Ile-de-France. 

Much  more  skillfully  executed  is  the  vault  of  St.-Victor  of  Marseille  (Fig.  20). 
Here  the  diagonals  are  much  reduced  in  width  and  have  only  a  single  set  of  vous- 
soirs. One  diagonal  was  constructed  before  the  other,  as  the  stone-cutting  at 
the  intersection  proves,  since  one  is  a  continuous  arch  against  which  the  two  half 


Fig.   18.      St.  -  Nicolas,  Moissac,  (Tarn-et-Garonne). 
Vault  of  Narthex. 


Fig.   19.      Cathedrale,  Frejus,   (Xar). 


Fig.   21.      St.  -  Guillicm-ii-DcMrl,  (.llerault). 
Vault  of  Narthex. 


i  ici.   iO.     St.  -  Mctor,  Marseille.      Vault  of  Porch. 


THE  CONSTRUCTION  OF  LOMBARD   AND  GOTHIC   ^  AULTS  13 

arches  of  the  other  abut.  The  vault  is  slightly  domed,  and  wall  ribs  are  em- 
ployed. This  is  the  earliest  vault  in  France  that  I  have  observed,  where  larger 
stone  courses  are  used  in  the  part  which  is  below  the  point  where  the  use  of  a  cerce 
became  necessary.  It  was  hence  obviously  erected  without  solid  centering.  The 
diagonals,  it  is  true,  tend  to  disappear,  but  this  fact  is  easily  explained.  In  the 
upper  part,  where  the  vault  required  centering,  the  diagonals  are  not  submerged, 
and  were  made  use  of  in  the  construction  of  the  vault.  Towards  the  springing 
the  rib  was  submerged  a  little  in  the  massive,  as  could  easily  be  done  where  the 
stones  of  the  vault  were  self-supporting,  to  accommodate  the  springing  of  the 
vault  to  the  profile  of  its  somewhat  clumsy  supports. 

At  St.-Guilhem-le-Desert,  Herault,  there  is  a  rib  vault  (Fig.  21)  of  a  different 
type,  which,  however,  exemplifies  precisely  the  same  principles.  The  vault  is  not 
domed,  but  its  restrained  dimensions  (4.30  x  4.90  meters)  and  the  thick  strong 
mortar  employed,  together  with  the  wall  ribs  (which  although  they  die  away, 
supported  the  centering  at  the  critical  points)  made  possible  its  construction 
without  solid  centering. 

Much  more  skilfully  constructed  are  the  vaults  of  the  cathedral  of  Frejus, 
Var  (Fig.  19),  which  are  probably  also  the  earliest  rib  vaults  extant  in  France, 
erected  over  a  nave.  The  compartments  are  nearly  square,  but  the  vaults  are 
more  domed  in  the  transverse  than  in  the  longitudinal  direction,  a  peculiarity 
thoroughly  Italian.  The  transverse  ribs  have  a  decidedly  horse-shoe  form,  while 
the  diagonals  and  wall  ribs  are  approximately  semicircular.  The  wall  arches 
die  away  towards  their  springing  as  at  St.-Guilhem-le-Desert.  The  masonry 
courses  tend  to  radiate  towards  the  key-stone,  the  earliest  example  of  this  expe- 
dient I  have  observed  outside  of  Italy.  These  vaults,  remarkably  similar  to 
those  of  Corneto-Tarquinia,  were  evidently  erected  by  builders  in  full  possession 
of  the  Italian  tradition.  The  builders  had  also  studied  to  advantage  the  Roman 
ruins  in  which  Frejus  is  so  rich,  as  is  shown  by  the  fact  that  the  ribs  of  the  vault 
are  received  on  a  heavy  pilaster,  or  spur  wall,  which  really  forms  an  effective 
buttress.  Thus  it  becomes  evident  that  the  masons  of  Frejus,  in  their  efforts  to 
erect  vaults  economically  and  scientifically,  besides  studying  Roman  methods  of 
buttressing,  had  imported  from  Italy  the  rib  vault,  entirely  extraneous  to  the 
local  style  of  the  Riviera;  and  that  they  had  done  this  because  that  form  offered 
over  all  the  others  the  great  structural  advantage  of  not  requiring  a  solid  tem- 
porary centering. 

The  French  master-builders  were  not  slow  to  perceive  the  fact  that  doming 
greatly  facilitated  the  construction  of  a  rib  vault  without  solid  centering.  The 
expedient  timidly  tried,  as  we  have  seen,  at  Rhuis  and  at  St. -Victor  of  Marseille, 
was  boldly  applied  at  Frejus  and  at  Ste. -Croix  of  Quimperle.  It  was  soon  taken 
up  and  carried  to  an  almost  exaggerated  extent  by  the  builders  of  the  Ile-de- 


^ 


14  THE    CONSTRUCTION   OF  LOMBARD  AND   GOTHIC   VAULTS 

France,  who  studied  to  give  their  vault  surfaces  the  greatest  inclination  possible. 
Thus  at  Belief ontaine,  Oise  (Fig.  23),  the  diagonals  are  pointed.  At  Bury,  Oise, 
the  opposite  expedient  is  tried  in  the  side  aisles  for  the  purpose  of  producing  the 
same  effect,  i.e.,  of  avoiding  horizontal  surfaces  in  the  vault.  The  curve  of  the 
diagonals  is  depressed,  the  main  arches  are  pointed,  the  transverse  arches  stilted, 
pointed,  and  loaded  (Fig.  24).  Thus  the  intersection  of  the  diagonals  is  lower 
than  the  crown  of  the  main  and  wall  arches  but  higher  than  that  of  the  trans- 
verse arches.     So  horizontal  surfaces  are  reduced  to  a  minimum. 

While  the  principle  of  doming  was  thus  taken  up  enthusiastically  from  the 
first,  the  French  builders  were  slow  to  recognize  the  advantages  of  wall  ribs,  which 
continued  to  be  frequently  dispensed  with  until  a  comparatively  late  epoch  of  the 
transition.  In  Italian  monuments  of  the  XI  and  XII  centuries,  wherever  vaults 
are  constructed  of  bricks,  wall  ribs  are  invariably  employed,  even  when  diagonal 
ribs  are  omitted;  in  vaults  constructed  of  stone,  on  the  other  hand,  wall  ribs  are 
invariably  lacking.  Since  in  France  vaults  are  always  constructed  of  stone,  I 
suspect  that  this  circumstance  is  not  without  bearing  upon  the  fact  that  wall 
ribs  were  frequently  omitted,  and  that  the  latter  were  considered  less  necessary 
in  ashlar  than  in  l)rick  constructions.  Nor  is  the  reason  hard  to  see.  When  wall 
ribs  are  omitted,  it  is  necessary  to  cut  the  inner  facing  of  the  wall  to  the  form  of 
an  arch,  so  that  the  vault  may  rest  upon  the  ledge  thus  formed.  In  brick  con- 
structions this  process  is  tedious,  since  a  great  quantity  of  bricks,  all  normally 
rectangular,  must  be  cut  to  the  required  form.  In  ashlar  constructions,  on  the 
other  hand,  the  stones  must  be  cut  in  any  event,  and,  since  they  are  larger  than 
bricks,  a  far  smaller  number  need  be  given  an  irregular  form.  Moreover,  a  wall 
rib  in  brick  may  be  constructed  without  centering  by  the  Byzantine  method, 
whereas  it  is  exceedingly  difficult  to  erect  in  this  manner  a  wall  rib  in  stone,  since 
the  weight  of  the  voussoirs  is  more  than  the  adhesion  of  the  mortar  suffices  to 
support.  For  these  reasons  in  the  early  period  vaults  in  bricks  were  constructed 
with  wall  ribs,  and  vaults  in  stone  without  wall  ribs.  Gradually,  however,  the 
advantages  of  the  wall  rib,  which  held  the  vault  against  the  wall  without  cutting 
its  surface  and  hence  weakening  it,  came  to  be  appreciated,  and  wall  ribs  were 
universally  adopted  even  in  ashlar  vaults. 

From  the  peculiarities  of  rib  vaults  above  enumerated,  and  from  many  others 
which  might  be  adduced,  it  is  evident  that  economy  of  centering  was  a  primary 
consideration  with  the  builders  of  the  transitional  and  Gothic  periods.  The 
principle,  it  is  true,  was  sometimes  violated,  especially  in  the  outlying  provinces; 
it  was  occasionally  modified  even  in  the  Ile-de-France.  But  these  exceptions 
only  make  clearer  the  force  of  the  rule,  that  the  great  advantage  of  the  rib  vault, 
the  reason  it  was  adopted  by  the  medieval  builders,  was  the  fact  that  it  could  be 
constructed  without  solid  centering. 


I 


Fui.   -H.     Sk.  -  Ciiiix,  Quimperle,  (Finistere). 


Fia.  23.      Prieure,  Bellefontaine,  about  i  kilometers 
from  Xampeol,  (Oise). 


Fig.   24.     Sts.  -  Pierre-Jiicqucs-et-Liicien,  Bury,  (Oi.se) 
North  side  aisle. 


Fig.    25.       Notre-Dame-du-l'orl.  CUTinoiit-lVrraiul, 
(Puy-de-D6me) .       North  side  aisle. 


THE  CONSTRUCTION   OF  LOMBARD   AND  GOTHIC   VAULTS  15 

The  most  conspicuous  examples  of  ribs  not  used  as  centering  are  found  in 
the  churches  of  Anjou,  where,  as  is  well  known,  ribs  were  applied,  almost  orna- 
mentally, to  vaults  essentially  domes  in  their  character.  Similarly  in  Xorniandy 
vaults  were  constructed  often  of  very  small  and  odd-shaped  stones  laid  in  irregu- 
lar courses  that  even  change  their  direction  at  right  angles.  In  churches  that 
are  still  open  to  the  cult  such  vaults  are  almost  invariably  covered  with  stucco, 
so  that  it  is  impossible  to  study  their  structure;  in  the  ruined  abbey  of  Ilambye, 
however,  certain  vaults  are  exposed  in  which  the  utterly  irregular  character  of 
the  courses  makes  it  evident  that  a  centering  must  have  been  employed.  In 
England  all  sorts  of  additional  ribs,  dividing  up  into  small  compartments  the 
space  to  be  vaulted,  were  introduced.  This  was  merely  carrying  the  French 
system  one  step  further,  but  the  extra  ribs  ended  by  degenerating  into  mere 
ornament,  largely  owing  to  the  fact  that  the  introduction  of  ridge-ribs  made  it 
necessary  that  the  doming  of  the  vaults  should  be  abandoned.  These  and  other 
similar  instances  of  later  vaults  constructed  with  centering  are  merely  isolated 
examples  of  peculiar  constructions;  throughout  the  Gothic  period  the  rib  vault 
continued  in  general  to  be  erected  without  solid  centering. 

The  desire  to  dispense  with  solid  centering  was  doubtless  the  reason  for  the 
adoption  of  the  rib  vault  by  the  French  builders  in  the  transitional  period.  Pre- 
vious to  its  introduction,  they  had  discovered  no  means  to  erect  vaults  without 
wooden  substructures.  The  familiar  hollow  spires  of  Loches  erected  on  the  corbel 
principle  are  the  most  conspicuous  attempt  at  such  a 
construction  that  I  know,  but  these  are  a  comparatively 
late  experiment  and  not  a  very  happy  one.  In  Auvergne 
and  Normandy  are  common  groin  vaults  which  instead  of 
being  domed  are  depressed  at  the  center  (Fig.  2(1).  This 
form  was  probably  designed  to  concentrate  the  thrust  on 
the  groins  and  relieve  the  transverse  and  longitudinal 
arches.     I  have  never  found  any  evidence  that  such  vaults 

were  constructed  without  centering,  although  their  form  would  permit  of  it.'  Such 
as  I  have  observed  are  of  orderless  rubl)le,  and  consequently  must  have  been 
constructed  on  a  solid  centering,  which  it  is  much  easier  to  shape  for  a  vault  of 
this  sort  than  for  a  domed  groin  vault  (Figs.  25,  28).  Ribs  were  often  applied  to 
barrel  vaults,  as  in  the  choir  of  Meils  Maisons,  Aisne  (Fig.  27).  In  such  vaults, 
however,  the  ribs  could  not  have  been  serviceable  as  centering  and  must  have  been 
useful  solely  to  strengthen  the  vault  and  prevent  any  possible  deformation.  Thus 
it  becomes  evident  that  of  the  various  forms  of  vault  known  to  the  transitional 
builders  at  the  time  they  adapted  the  rib  vaults,  the  latter  only  could  be  erected 
without  solid  centering.     Domed  groin  vaults  form   the  only  exception   to  this 

'  See  what  has  been  said  above  of  Bury. 


16  THE   CONSTRUCTION  OF  LOMBARD   AND   GOTHIC   VAULTS 

rule.  Such  vaults  were  never  common  in  France,  but  isolated  examples  of  the 
construction  exist.  The  vaults  of  the  side  aisles  at  Morienval  are  modern,  but 
are  probably  correctly  restored  as  domed.  The  groin  vaults  of  the  crypt  of  St.- 
IVIedard  at  Soissons  are  also  domed.  These  and  other  instances  show  that  the 
French  builders  became  acciuainted  at  al)out  the  same  time  with  both  the  Lom- 
bard methods  for  reducing  centering.  They  seem  to  have  consistently  preferred 
the  rib  to  the  domed  groin  construction,  however,  even  over  small  areas;  and  the 
reason  was  douljtless  that  the  rib  construction  adapted  itself  better  to  stone,  the 
building  material  universally  employed  in  France.  Stones  being  heavier  than 
bricks  placed  a  greater  weight  on  the  centering  underneath  the  groin  during  con- 
struction; hence  it  was  desirable  to  make  this  centering  a  rigid  stone  arch  rather 
than  a  flimsy  wooden  sub-structure. 
-^-i  That  the  ribs  oj^  rib  vault,  especially  in  the  Gothic  period,  came  to  assume 

other  functions  besides  that  of  serving  as  a  centering  during  the  construction,  is 
not  to  be  denied,  grossly  as  the  importance  of  these  functions  has  been  exaggerated 
by  certain  writers.  The  ribs  doubtless  materially  strengthened  the  groins,  which 
are  the  weak  point  of  the  vault  surface;  they  also  tended  to  prevent  deformations, 
removed  all  danger  of  the  cells  slipping,  and  re-enforced  the  angle  joints.  Once 
completed,  however,  the  vault  was  no  longer  absolutely  dependent  upon  them  for 
its  stability,  and  in  the  majority  of  cases  it  is  probable  that  the  ribs  could  be 
removed  from  beneath  Gothic  vaults  without  injury  to  the  vaults  themselves. 

In  the  ruined  abbey  of  Longpont,  Aisne  (Figs.  29,  30,  31,  32,  35),  there  are 
vaults  whose  massive  still  stands  although  the  ribs  have  fallen  from  beneath 
them.  Groin  vaults  can  be  self-supporting  and  sufficiently  strong  as  every  one 
knows  (Fig.  3i) ;  hence  the  one  great  advantage  of  the  rib  over  the  groin  form 
was  its  greater  ease  of  construction. 
-  /  A  similar  consideration  was  undoubtedly  an  important  factor  in  causing  the 
Gothic  architects  to  adopt  the  pointed  arch,  since  this  form  contains  more^  verti- 
cal and  less  horizontal  surfaces  than  a  round  arch.  It  can  consequently  be  erected 
with  lighter  centering.  And  in  Gothic  pointed  arches  the  joints  do  not  radiate 
towards  the  center,  the  voussoirs  being  cut  normal  to  the  intrados  or  even  less 
(Fig.  32).  Consequently  the  weight  of  each  stone,  even  during  consJruction, 
was  carried  largely  by  the  one  below  it  instead  of  by  the  centering. 

Thus  every  detail  of  Gothic  rib  vaults  was  governed  by  strict  logic  of  con- 
struction and  disposed  with  a  view  to  the  greatest  possible  economy  of  cen- 
tering. This  same  generating  principle  caused  the  introduction  of  the  rib 
vault  in  the  Ile-de-France  in  the  transitional  period;  governed  each  new  form 
that  was  given  it,  every  peculiarity  that  it  assumed;  and  finally,  through  the 
perfection  of  the  rib  vault,  led  to  the  invention  of  Gothic  architecture.  It  is 
evident  that  this  process  of  construction  is  of  the  gravest  importance  for  the 


Fig.    27.      St.-Croix,  Vicils-Maisons,  (Aisne).      Choir. 


Fig.    28.      St.  -  Nicolas,  Caen,  (Calvados). 
South  side  aisle. 


Fig.   29.      Abbaye,  Longpont,  (.\isne). 


Fig.   30.      Abbaye,  Longpont,  (Aisne). 
South  side  aisle. 


Fig.   31.      .\bbaye,  Longpont,  (Aisne). 
South  side  aisle. 


Fig.   32.      .\l)ba^e,  Loiigi)ont,  (.\isiie). 
Xortli  side  aisle. 


Fio.  33.      S.  Felice,  Cimitile,  (Caserta),      Crypt. 


Fig.  34.      St.-Morent,  Margivul,  (.Visne).      Crossing. 


Fig.  35.      Abbaye,  Longpont,  (.\isne).      Vault.s  of  mirth  .siilc  aisli 


Fig.  3G.      .\bbazia,  near  Sesto  Calende,  (Milano).      Crypt. 


THE   CONSTRUCTION  OF  LOMBARD   AND   GOTHIC   VAULTS  17 

history  of  art,  and  is  one  with  which  the  student  of  medieval  architecture  must 
seriously  reckon. 

V 

A  STUDY  of  the  process  of  construction  throws  an  equal  light  on  the  early  rib 
vaults  of  Lombardy.  It  was  in  Lombardy  that  this  type  of  vault  originated, 
and  when  the  method  of  construction  which  we  have  learned  from  a  study  of  the 
French  vaults  is  borne  in  mind,  it  is  easy  to  trace  the  various  steps  in  the  evolu- 
tion of  this  motive,  so  significant  for  the  history  of  medieval  art.  The  Lombard 
monuments  will  also  furnish  the  clearest  sort  of  proof  that  the  rib  vault  originated 
in  the  desire  to  economize  centering,  and  was  ever  employed  with  this  sinojo  ond 
in  view. 

Whereas  in  France  during  the  Carlovingian  and  Romanesque  periods  there 
had  been  only  one  method  employed  for  constructing  vaults,  that  of  solid  center- 
ing, in  Lombardy  on  the  other  hand,  from  the  VI  century  to  the  XIII,  there 
existed  side  by  side  two  traditions:  the  Byzantine,  by  which  domed  groin  vaults, 
usually  with  wall  and  transverse  ribs,  were  constructed  on  a  light  centering;  and 
the  Latin,  by  which  undomed  groin  vaults,  barrel  vaults  and  cupolas  were  erected 
with  the  aid  of  a  complete  centering. 

To  prove  the  survival  of  the  Byzantine  type  during  the  dark  ages,  it  is  suffi- 
cient to  cite  the  domical  groin  vaults  of  the  eastern  bays  of  the  side  aisles  of  Agliate 
(Milano),'  and  the  groin  vault  that  covers  the  nave  of  S.  Fedelino  on  the  lake  of 
Mezzola. 

Of  the  Latin  tradition  we  find  examples  in  the  eastern  bays  of  the  side  aisles 
of  S.  Ambrogio  at  Milan,  and  in  S.  Satiro  of  the  same  city.  Moreover,  a  great 
number  of  crypts  of  the  VI  to  X  centuries  throughout  Italy  are  covered  with 
groin  vaults  erected  on  a  curious  principle  that  reiquires  a  word  of  explana- 
tion. At  S.  Salvatore  of  Brescia,  it  will  be  remembered,  the  columns  of  the  crypt 
bore  arches;  these  arches  carried  walls,  parallel  the  one  to  the  other,  on  which 
were  placed  slabs  of  stone  forming  the  pavement  of  the  choir.  That  is,  the  crypt 
was  not  vaulted  at  all,  but  covered  with  a  series  of  lintels  supported  on  arches. 
Such  a  system  is  the  basis  of  the  construction  of  a  vast  number  of  crypts  erected 
throughout  Italy  not  only  during  the  dark  ages,  but  in  the  eleventh  and  twelfth 
centuries.  The  state  of  ruin  into  which  has  fallen  the  crypt  of  S.  Felice  at  Cimi- 
tile  (Napoli)  makes  it  easy  to  understand  the  construction.  Here  arches  were 
sprung  from  every  column  in  four  directions,  and  the  wall  continued  upward 
above  them  (Fig.  33).  Then  in  the  quadrangles  so  formed  were  l)uilt  on  centers 
groin  vaults,  merely  stuck  on  to  the  sides  of  the  walls  above  the  arches.  On  the 
abaci  of  the  capitals,  the  vaults  nearly  or  quite  submerged  the  arches,  there  not 
'  These  have  been  restored  but  apparently  in  their  original  form. 


V 


L^ 


vj 


18  THE   CONSTRUCTION  OF  LOMBARD  AND   GOTHIC  VAULTS 

being  sufficient  space  for  these  to  project;  near  the  crown,  on  the  other  hand, 
the  arches  were  very  saHent.  Transverse  ribs  thus  dying  away  towards  the 
springing  are  found  for  the  first  time,  I  beheve,  in  the  transept  ends  of  the  tomb 
of  Galla  Placidia  at  Ravenna,  but  they  were  here  used  in  connection  with  a  barrel, 
not  a  groin  vault.  The  motive  was  of  great  effect  used  decoratively,  and,  applied 
to  arches,  became  characteristic  of  the  Lombard  style  of  the  XI  and  XII 
centuries  —  witness  Santa  Maria  Maggiore  of  Lomello,  and  S.  Savino  of  Piacenza. 
As  the  transverse  arches  died  away  towards  the  springing,  the  groin  in  its  lower 
part  was  worked  to  a  sharp  point  to  carry  up  the  angle  of  the  capital.  In  certain 
instances,  especially  in  later  crypts  such  as  those  of  Gravedona  or  Sesto  Calende 
(Fig.  36),  the  vaults  are  domed,  and  were  probably  constructed  without  solid 
centering;  the  massive  may  even  be  carried  on  the  arches  which  in  that  case 
would  become  ribs.  But  wherever  I  have  been  able  to  study  the  earlier  vaults 
(in  the  majority  of  cases  it  is  of  course  impossible  to  investigate  without  damag- 
ing the  building)  the  construction  is  like  that  of  Cimitile,  i.e.,  the  vaults  are  not 
carried  on  top  of  the  transverse  arches  but  are  merely  plastered  against  them. 
Whether  constructed  with  or  without  centering,  such  are  not  true  Byzantine 
vaults. 

Barrel  vaults,  cloistered  vaults,  and  half  domes  were,  I  believe,  generally  con- 
structed on  centering,  not  only  during  the  dark  ages  but  in  the  XI  and 
XII  centuries  as  well.  The  structure  of  most  of  them  is  unfortunately  inacces- 
sible, but  those  I  have  been  able  to  observe  seem  to  be  constructed  of  loose  mate- 
rials laid  in  such  a  way  as  to  preclude  the  possibihty  of  construction  without 
centering.' 

Early  in  the  XI  century  new  principles  of  construction  came  to  be  adopted 
by  the  Lombard  master-builders.  Scarcity  of  wood  seems  to  have  been  the  cause 
which  induced  the  architects  to  abandon  the  traditional  methods  of  the  Car- 
lovingian  builders.  A  veritable  architectural  revolution  ensued,  of  which,  however, 
we  have  here  to  speak  of  only  one  phase,  though  that,  perhaps,  the  most  significant 
—  I  mean  the  practical  construction  of  vaults. 

If  we  survey  those  monuments  of  the  XI  and  XII  centuries  which  are 
commonly  designated  by  the  term  Lombard,  we  observe  that  the  geographical 
distribution  of  the  school  is  peculiarly  irregular.  The  churches  of  Corneto-Tar- 
quinia  on  the  southern  confines  of  the  Maremma  resemble  those  of  Milan  much 
more  closely  than  do  those  erected  at  Como  only  some  forty  kilometers  distant. 
Such  a  state  of  affairs  is  entirely  different  from  conditions  in  France,  for  example, 

'  In  the  illustrations,  Figs.  37,  38,  39,  40,  -11,  42,  43,  I  give  a  series  of  photographs  illustrating  the  types 
of  vault  above  described,  and  especially  the  parallel  use  of  domed  and  non-domed  groin  vaults  in  crypts  and 
other  portions  of  the  edifice  in  monuments  from  all  regions  of  Lombardy  from  the  VIII  to  the  XII  century. 
Since  the  photographs  speak  sufficiently  clearly  for  themselves,  it  will  not  be  necessary  to  describe  them. 


Fig.  37.      S.  Ketro  al  Monte,  near  Civate,  (Como) .      Crypt. 


Fig.  38.      S.  Teoiloro,  Tavia.      Cr.vpt. 


Fig.  39.      S.  Stefano,  Lenno,  (Como).     Crypt. 


Fig.  40.      Duomo  \'ccchio   Hrcscia.      Crypt. 


Fig.  il.      S.  Maria  del  Solario,  Brescia.      Vault  in  crypt. 


Fig.  ii.      Madonna  del  (astello.  .Mmenno 
S.  Salvatore,  (Bergamo). 


Fig.  43.      S.  Vincenzo,  (jalliano,  near  Cantii,  (Como). 
Crypt. 


THE   CONSTRUCTION   OF  LOMBARD   AND   GOTHIC  VAULTS        19 

where  all  the  contemporaneous  monuments  of  a  given  region  closely  resemble 
each  other  and  form  a  local  school.  The  explanation  is  that,  whereas  in  France, 
a  country  of  broad  flat  uniform  plains,  in  any  given  province  tlie  building 
materials  available  were  about  the  same  everywhere,  in  Italy,  cut  up  by  moun- 
tains into  regions  of  varied  geological  character,  they  differed  widely,  even  in 
localities  not  far  removed  one  from  the  other.  The  development  of  Lombard 
architecture  was  determined  by  the  materials  the  l)uilders  found  available. 

Lombard  buildings  were  constructed  of  brick,  stone,  and  wood.  According 
as  one  or  the  other  of  these  materials  was  superabundant  or  failing,  the  archi- 
tecture shaped  itself.  It  was  to  dispense  with  wood  that  the  builders  sought  to 
erect  vaulted  edifices.  The  proofs  are  many.  At  Como  and  in  other  localities 
at  the  foot  of  the  Alps  where  wood  was  abundant,  vaulted  construction  was  long 
avoided  and  never  more  than  partially  adopted.  In  the  whole  province  of  Como 
not  a  single  vaulted  Romanesque  church  has  come  down  to  us,  and  doubtless 
none  was  ever  erected. 

During  the  XI  century,  this  school,  which  has  been  suspected  of  being 
the  center  from  which  radiated  the  influence  of  the  Lombard  master-builders, 
was  notably  behind  all  the  neighboring  schools  in  regard  to  everything  that  touches 
vaulted  construction.  Moreover,  the  hard,  flint-like  stone  which  was  the  build- 
ing material  usually  adopted  in  this  region,  was  quite  unfitted  for  the  construction 
of  vaults,  being  too  hard  and  brittle  to  be  shaped  accurately  into  voussoirs  or 
even  into  regular  courses. 

In  all  the  Lombardy  plain,  however,  throughout  that  vast  triangle  the  sides 
of  which  are  determined  by  the  Alps,  the  Apennines,  and  the  Adriatic,  brick  was 
the  building  material  which  the  builders  found  themselves  forced  to  use.  This 
vast  alluvial  region  is  practically  without  stone,  while  clays  for  terra  cottas  and 
bricks  abound.  Wood  is  scarce,  and  even  to-day  is  employed  with  parsimony.' 
In  the  XI  century  it  is  probable  that  trees  were  as  scarce  in  the  neighbor- 
hood of  Milan  as  they  are  now.  Moreover,  in  those  times  it  was  not  easy  to 
import  timber.  The  frequent  wars  with  the  surrounding  city  states  must  have 
totally  interrupted  for  long  periods  any  peaceful  commerce;  the  roads  were  doubt- 
less very  bad;  and  means  of  transportation  aside  from  the  most  primitive  there 
were  none.  We  can  imagine  therefore  that  at  Milan  the  price  of  wood  was  so 
high  as  to  be  well-nigh  prohibitive.  The  architects  had  to  find  a  means  of  roofing 
their  edifices  with  bricks,  and  of  erecting  vaults  without  the  use  of  elaborate 

'  The  fires  which  devastated  Milan  in  1071  and  1075  were  doubtless  fed  by  the  thatched  roofs  with  which 
the  houses  in  that  epoch  were  covered.  That  brick  was  commonly  employed  to  construct  tlie  walls  of  even 
modest  edifices  in  Lombard  towns  during  the  XI  and  XII  centuries  is  demonstrated  by  the  heaps  of 
brick  still  existing  at  Lodi  Vecchio.  Medieval  diplomas  make  frequent  mention  of  woods  which  were  evi- 
dently regarded  as  exceedingly  valuable  possessions.  It  is  probable  that  the  trees  were  seldom  allowed  to 
grow  large  enough  to  supply  timbers  for  a  church  roof. 


20         THE   CONSTRUCTION  OF  LOMBARD   AND   GOTHIC  VAULTS 

centering.  To  do  this  they  had  recourse  to  the  rib  vault.  They  dispensed  in 
many  cases  even  with  the  wooden  roof  over  their  vaults  which  the  French  builders 
almost  invariably  used.  In  the  Annunziata  of  Corneto-Tarquinia  a  solid  bed  of 
mortar  is  laid  on  the  upper  surface  of  the  vaults  and  is  worked  to  the  form  of  a 
gable  on  which  the  tiles  are  laid  directly.  At  S.  Savino  of  Piacenza,  before  the 
lamentable  restoration,  the  vaults  supported  a  series  of  brick  arches  which  carried 
the  tiles  without  the  use  of  any  wood.  That  the  builders  thus  carried  their  sav- 
ing of  wood  so  far  as  to  place  all  this  vast  weight,  in  a  most  dangerous  and  daring 
manner,  directly  on  the  great  vaults,  which  even  without  extra  charge  were  insuf- 
ficiently buttressed,  shows  that  economy  of  wood  was  carried  to  the  last  degree. 
At  Modena,  where  wood  was  probably  not  so  costly,  perhaps  because  of  forests 
still  existing  in  the  Apennines,"  the  cathedral  of  the  XII  century  was  roofed 
in  wood;  at  Bologna,  where  wood  was  scarce,  vaults  quite  similar  to  those  of 
Milan  were  erected  much  earlier  in  the  church  of  Santo  Stefano. 

Corneto-Tarquinia  stands  in  the  midst  of  a  plain  on  which  grows  no  timber. 
Even  to-day  the  poorest  houses  are  vaulted;  wooden  ceilings  are  unknown.  On 
the  other  hand  there  is  an  abundance  of  stone,  easily  cut,  in  every  way  adapted 
for  building.  The  builders  eagerly  abandoned  the  wooden-roofed  basilica,  to 
substitute  therefor  Lombard  rib  vaults  easily  erected  with  a  minimum  center- 
ing (Fig.  45).  Thus  it  is  evident  that  the  scarcity  of  timber  in  certain  parts  of 
Italy  drove  the  builders  to  adapt  vault  construction  and  discover  devices  to  erect 
vaults  without  the  use  of  wooden  centering. 

Milan  and  the  plain  about  it  was  evidently  the  center  in  which  was  developed 
and  from  which  radiated  the  new  method  of  construction.  It  took  the  better 
part  of  a  century  to  perfect  the  system,  and  the  goal  was  arrived  at  only  by  a  long 
series  of  experiments  with  many  hesitations  and  even  back-slidings.  The  first 
step  was  to  apply  the  Byzantine  domed  rib  vaults,  the  tradition  of  constructing 
which  with  light  centering  had  never,  as  we  have  seen,  died  out,  to  the  side  aisles. 
Next  transverse  arches  were  thrown  across  the  nave.  By  means  of  these  arches 
the  heavier  timbers  that  would  otherwise  have  been  required  for  the  roof  could 
be  dispensed  with.  As  early  as  c.  1025  we  find  that  the  art  of  building  had  already 
arrived  at  this  point  at  Lomello.  The  third  step  was  to  vault  the  nave.  It  must 
be  remembered  that  to  do  this  with  centering  offered  no  difficulty  for  the  Lom- 
bard builders.  Even  in  the  IX  century  the  choirs  of  S.  Ambrogio  of  Milan 
and  of  Agliate  had  been  successfully  barrel-vaulted.  But  the  point  was  to  build 
the  nave  vaults  without  centering,  or  rather  with  a  light  and  inexpensive  one. 
At  Stradella  it  was  evidently  the  intention  to  erect  such  groin  vaults  on  a  very 
oblong  plan.  With  a  Byzantine  domed  groin  vault,  it  was  almost  as  easy  to 
cover  an  oblong  as  a  square  plan,  one  of  the  great  advantages  of  this  system,  with 

'  See  the  diploma  of  Berengar  I,  899  ed.  Muratori  A.  I.  M.  A.,  ed.  A.  IV,  279. 


Fig.  4-1.      S.  Ambrogio,  Milano. 


■'- 

1 

.•■^•i^ 

m--':'^ 

) 

y 

I 

1 

1 
1 

^Wt 

■^'  ^^'    •- 

Fig.  45.      S.  Giacomo,  Cometo-Tarquinia,  (Roma). 


Fig.  46.      S.  Saviiui,  Piacenza.      Nave. 


THE   CONSTRUCTION  OF  LOMBARD   AND   GOTHIC  VAULTS  21 

its  absence  of  wooden  mould,  being  its  superior  flexibility.  In  earlier  times, 
when  vaults  were  confined  to  crypts  and  side  aisles,  they  had  been,  as  a  matter 
of  fact,  usually  erected  on  a  plan  approximately  square;  but  when  the  builders 
had  need  of  an  oblong  vault  they  did  not  hesitate  to  build  it.  It  was  not  the 
shape,  but  the  size  of  the  nave  vaults  which  caused  the  difficulty,  for  it  was  a 
delicate  task  to  erect  on  a  cerce  the  long  courses  necessitated  by  vaults  of  such 
dimensions.  The  vaults  at  Stradella,  though  projected,  were  never  erected;  nor 
is  there  proof  that  during  the  XI  century  any  similar  vaults  were  ever  exe- 
cuted. 

At  Sannazzaro  Sesia,  in  1040,  however,  the  nave  was  actually  vaulted,  the 
vaults  having  a  full  set  of  ribs  including  diagonals.  The  reason  for  the  intro- 
duction of  ribs  in  these  nave  vaults  it  is  easy  to  see.  Owing  to  the  considerable 
size  of  the  nave  and  the  weight  that  had  to  be  carried  by  the  centerings  under 
the  groins  during  execution,  it  was  found  that  if  a  groin  vault  was  to  be  erected 
these  centerings  must  be  made  heavy  and  cumbrous.  It  was  less  expensive  to 
erect  a  light  wooden  arch,  sufficient  to  serve  as  centering  for  the  heavy  brick 
diagonals;  these  once  erected  served  as  a  firm  and  sufficient  centering  for  the 
vault.  Moreover,  after  the  vault  was  completed,  the  ribs  strengthened  it,  pre- 
vented cracks  at  the  groins,  and  tended  to  oppose  deformation,  precisely  as  do  the 
ribs  of  a  French  vault.  The  motive  once  found  for  structural  reasons  seems  to 
have  pleased  aesthetically  also;  at  any  rate,  rib  vaults  were  introduced  in  the 
returned  aisle  of  Sannazzaro  Sesia  and  in  the  narthex  of  S.  Ambrogio,  although 
the  spaces  to  be  vaulted  were  no  larger  than  in  the  groin-vaulted  side  aisles." 

There  remained  only  one  further  step  to  be  taken  in  the  development  of  the 
Lombard  style,  that  of  combining  the  rib  vault  as  developed  at  Sannazzaro  Sesia 
with  the  alternate  system  as  developed  in  connection  with  the  transverse  arch 
at  Lomello,  Calvenzano,  and  Lodi  Vecchio.  The  advantages  of  this  combination 
(Fig.  46)  were  two-fold.  In  the  first  place  it  made  it  possible  to  vault  the  space 
comprised  by  two  bays  with  four  centerings  (erected  under  the  various  arches) 
instead  of  the  seven  that  would  otherwise  be  required.  In  the  second  place  it 
raised  the  crossing  of  the  diagonals  considerably  (the  arches  all  being  semicircular), 
thus  giving  the  vault  surface  a  more  domical  form  and  one  conscfiuently  easier 

'Nevertheless  the  rule  holds  that  the  Lombards  never  adopted  the  rib  vault  with  eutlnisiasni.  Tliere 
is  not  extant  a  single  Lombard  church  where  it  is  used  throughout.  In  general,  wlierevor  the  l>uiidiTs  dared, 
they  omitted  the  diagonal  ribs.  Thus  the  side  aisles  were  always  covered  with  groin  vaults,  and  rib  vaults 
were  at  a  comparatively  early  date  abandoned  even  in  naves.  At  S.  Savino  of  Piaccnza.  the  two  eastern 
bays  of  the  nave  are  rib-vaulted,  but  the  later  western  bay  has  a  groin  vault.  The  l)uildcrs  appear  to  have 
abandoned  rib  vaults  the  moment  they  dared  to  construct  domical  groin  vaults  (which  also  did  not  require 
centering)  of  the  required  size  without  diagonal  ribs.  Thus  it  was  the  knowledge  of  how  to  construct  groin 
vaults  without  centering  —  a  knowledge  which  the  French  builders  did  not  possess  —  that  prevented  the 
Lombards  from  developing  to  its  utmost  possibilities  the  rib  vault. 


22  THE   CONSTRUCTION   OF  LOMBARD  AND   GOTHIC   VAULTS 

to  construct.  On  the  other  hand,  the  courses  between  the  diagonals  and  the 
transverse  ribs  became  longer,  but  no  longer  than  those  between  the  wall  arches 
and  the  diagonals  in  either  case.  The  first  extant  monument  where  this  system 
is  applied  is  S.  Ambrogio  of  Milan  (Fig.  44). 

The  wars  of  the  XII  century,  culminating  in  the  destruction  of  Milan  in 
1162,  were  fatal  to  the  development  of  Lombard  architecture,  and  there  are 
scarcely  enough  monuments  extant  at  Milan  to  enable  us  to  trace  the  causes  of 
the  decline  into  which  it  fell.  Probably  lack  of  abutment  for  the  vaults  was  the 
principal  one,  and  that  which  prevented  the  Lombard  builders  from  anticipating 
the  discovery  of  Gothic.  The  thrust  of  vaults  they  seem  never  to  have  fully 
understood,  nor  to  have  realized  that  the  resultant  of  the  thrusts  of  a  vault  is  a 
curve,  and  that  consequently  piers  supporting  a  vault  should  be  stepped  out- 
wards towards  their  base.  Buttresses  are  sometimes  applied  to  the  outside  walls, 
it  is  true,  but  they  are  never  sufficiently  developed  for  a  structure  in  brick.  The 
abutting  walls  built  across  the  transverse  arches  of  the  galleries  to  reinforce  the 
nave  vaults  were  always  used  in  an  illogical  manner;  they  appear  to  have  been 
copied  from  Roman  edifices  without  much  understanding  of  their  real  function. 
At  S.  Ambrogio  they  seem  to  have  been  originally  applied  to  each  bay  indiffer- 
ently, although  the  system  was  alternate;  at  S.  Savino  of  Piacenza,  Sagra  S. 
Michele,  and  Rivolta  d'Adda,  they  were  placed  with  something  more  like  caprice 
than  intelligent  experiment.  The  Lombard  builders  were  logical  as  a  rule,  almost 
as  logical  as  the  early  Gothic  architects,  and  I  realize  that  it  is  dangerous  to 
reproach  them  with  inconsequence  merely  because  their  aims  are  not  clear.  In 
this  case,  however,  the  result  seems  to  justify  the  charge,  for  their  vaults  have 
proved  almost  without  exception  to  be  insecure.  Even  the  use  of  tie-rods  in  wood 
and  metal  —  a  tradition  inherited  from  the  Byzantines  —  has  failed  to  hold  them 
together.  In  only  two  points  have  I  observed  anything  like  the  subtle  under- 
standing of  the  principles  of  equilibrium  which  guided  the  northern  architects. 
One  is  found  at  S.  Ambrogio,  Calvenzano,  and  in  certain  other  edifices  where  the 
alternate  system  is  used,  and  consists  in  making  the  responds  of  the  side  aisles 
alternately  heavier  and  lighter.  The  builders  have  evidently  reasoned  out  that 
the  thrust  against  the  alternate  piers  is  transmitted  across  the  buttressing  vaults 
of  gallery  or  aisle  and  ends  by  being  exerted  against  the  outside  wall,  which  is 
accordingly  strengthened  at  the  critical  point.  The  builders  of  the  cathedral  of 
Paris,  nearly  a  century  later,  made  the  same  observation.  The  Lombard  builders, 
however,  did  not  perceive  that  it  would  have  been  better  to  strengthen  the  out- 
side, rather  than  the  inside,  face  of  the  wall. 

The  second  point  of  subtlety  was  the  use  of  wooden  chains  in  the  walls.  This 
is  an  old  Byzantine  tradition,  admirable  in  theory  but  not  always  successful  in 
practice.     Indeed,  Mr.  de  Dartein  has  showed  how  disastrous  its  effects  frequently 


THE  CONSTRUCTION  OF  LOMBARD  AND  GOTHIC   VAULTS  23 

were  in  Lombard  buildings.  Wood  is  a  perishable  material,  which  in  the  course 
of  time  rots  and  disappears.  If  then  the  masonry  actually  rest  upon  it,  so  that 
the  disintegration  of  the  wood  be  liable  to  cause  weakness  or  lesions,  the  construc- 
tion is  vicious.  If,  however,  it  be  comparatively  so  small  a  i)art  of  the  wall  area 
that  this  is  sufficiently  strong  when  the  wood  has  disappeared,  the  construction 
is  ingenious  and  admirable.  These  wooden  chains  are  in  this  case  merely  designed 
to  bind  the  masonry  together  and  prevent  cracks  during  the  period  in  which  the 
freshly  laid  mortar  is  liable  to  compression  and  the  masonry  to  unequal  settle- 
ment. 

About  the  year  1120  rib  vaults  of  the  true  Lombard  type,  such  as  we  find 
at  S.  Ambrogio,  seem  to  have  passed  out  of  use.  Since  they  had  been  found 
unstable,  many  builders  returned  to  the  old  wooden  roof,  usually  supported  on 
transverse  arches;  those  who  were  still  forced  by  the  scarcity  of  timber  to  use 
vaults,  discovered  that  bj^  making  the  shells  very  thin,  groin  vaults  could  be 
erected,  even  over  a  nave,  on  a  very  light  centering.  The  ribs,  therefore,  were 
much  reduced  in  size  (S.  Pietro  in  Ciel  d'Oro  of  Pavia)  and  finally  abandoned 
altogether  (S.  Lanfranco  of  the  same  city).  Moreover,  with  the  constructive  skill 
the  builders  had  now  acquired  they  became  quite  indifferent  to  the  economical 
advantages  of  a  square  plan,  and  learned  to  construct  vaults  on  oblong  plans 
with  almost  as  light  a  centering.  So  the  alternate  system  came  to  be  gradually 
abandoned. 

The  history  of  the  rib  vault  in  Lombardy  proves,  therefore,  that  this  con- 
struction originated  as  a  modification  of  the  domed  groin  vault  erected  without 
solid  centering;  that  the  diagonal  ribs  were  added  merely  to  facilitate  the  con- 
struction of  vaults  of  large  dimensions;  and  that  rib  vaults  were  employed  only 
in  those  regions  of  Italy  where  wood  was  rare  and  expensive,  vaults  erected  on  a 
full  centering  being  employed  elsewhere. 

Thus  it  is  clear  that  the  striving  to  economize  wooden  centering  in  the  con-  i^-^ 
struction  of  vaults,  plays  a  very  important  role  in  the  history  of  medieval 
architecture.  The  Romans  displayed  great  ingenuity  in  devising  means  to 
accomplish  this  end,  erecting  centerings  which  were  not  merely  temporary,  but 
part  of  the  completed  vault;  the  Byzantine  architects  with  the  same  object  in 
view  invented  the  domed  groin  vault,  which  became  known  in  Italy  from  an 
early  period  and  continued  in  use,  together  with  other  types  of  vaidt  constructed 
on  solid  centering,  throughout  the  Carlovingian  period.  In  the  XI  century  the 
scarcity  of  wood  in  the  Lombard  plain  led  to  the  invention  of  the  rib  vault  and  its 
introduction  in  the  naves  of  certain  churches,  since  the  construction  of  domed 
groin  vaults  in  such  a  position  exceeded  the  skill  of  the  early  builders.  Only 
exceptionally  was  the  rib  vault  employed  except  over  naves.  It  was  never 
adopted  in  those  regions  of  Italy  w^here  wood  was  abundant,  and  was  generally 


24  THE   CONSTRUCTION   OF  LOMBARD  AND   GOTHIC   VAULTS 

abandoned  when  other  means  of  erecting  nave  vaults  without  centering  were 
discovered.  The  desire  to  economize  centering  led  the  French  builders  to  adopt 
the  Lombard  rib  vault  in  preference  to  the  other  forms  of  vault  to  them  known, 
all  of  which  required  solid  centering.  Applied  at  first  generally  beneath  towers, 
in  amljulatories,  or  in  other  positions  where  a  solid  centering  was  especially  incon- 
venient, it  came  gradually  to  supplant  all  other  types  of  vault.  As  a  direct  result 
of  its  development  arose  that  new  architecture  which  is  called  Gothic.  Through- 
out the  Gothic  period  rib  vaults  continued,  save  in  exceptional  cases,  to  be  erected 
without  solid  centering. 

Evidently  the  fact  that  rib  vaults  were  thus  constructed  is  one  of  no  mean 
importance  for  the  history  of  art. 


APPENDIX 

ONE  of  the  chief  advantages  of  the  rib  vault  was  the  fact  that  it  could  be 
applied  not  only  to  quadripartite  rectan<fular  spaces  but  equally  well  to 
irregular  plans,  to  the  trapezoidal  compartments  of  an  ambulatory  or 
annular  gallery,  to  the  semi-circular  vault  of  an  apse,  or  to  the  polygonal  vault  of 
a  chevet.  It  also  lent  itself  with  facility  to  the  sexpartite  form  of  a  vault.  The 
warped  and  ungeometrical  surfaces  of  any  of  these  irregular  types  of  vault 
would  have  rendered  exceedingly  difficult  and  expensive  their  construction  on 
solid  centering.  The  system  of  ribs,  on  the  other  hand,  adapted  itself  with  ease 
to  such  constructions.  Building  free-hand  and  without  centering,  the  masons 
were  able  to  depart  from  geometric  forms  at  their  will. 

The  experiments  of  the  French  builders  with  vaults  of  such  types  have  been 
so  often  described  that  they  need  here  only  be  referred  to.  Every  student  of 
medieval  art  is  familiar  with  these  typical  forms  of  Gothic  architecture  and  is 
aware  of  the  ease  and  fluency  with  which  the  architects  finally  learned  to  con- 
struct them.  It_jvas  only  the_JaeMthat  such  vaults  could  be  erected  without 
centering  that  made  Gothic  architecture  possible.  This  point  can  not  be  illus- 
trated more  forcibly  than  by  a  study  of  the  annular  vaults  erected  in  those  parts 
of  Lombardy,  where,  owing  to  the  abundance  of  timber,  the  builders  had  not 
adopted  the  rib  vault.  I  shall  describe  in  some  detail  in  this  Appendix  a  series 
of  such  constructions,  since  they  make  it  evident  that  rib  vaults  were  employed 
only  to  economize  centering,  and  were  seldom  if  ever  introduced  merely  with  a 
view  to  increasing  the  elegance  of  the  design.  From  these  vaults  it  will  also  be 
possible  to  illustrate  the  fact  that  the  Lombard  builders  often  used  simultaneovisly 
the  two  methods  of  construction:  that  with,  and  that  without,  a  solid  centering. 

The  vaults  of  the  ambulatory  of  Santo  Stefano  at  Verona  (Fig.  48)  are  the 
oldest  annular  vaults  of  Lombardy  that  I  know.  They  have  been  modernized, 
but  not  so  completely  that  their  original  form  can  not  be  recognized.  The  ambu- 
latory is  divided  into  rectangular  compartments  by  means  of  wedge-shaped  trans- 
verse arches,  really  triangular  barrel  vaults.  The  rectangular  spaces  were  covered 
with  domed  groin  vaults  erected  without  centering.  The  crypt  of  the  ambulatory 
is  covered  w'ith  a  barrel  vault  and  w'ith  one  groin  vault  at  the  east  end,  all  erected 
with  centering  (Fig.  47). 

In  the  Rotonda  of  Brescia  the  arrangement  is  different.  The  circular  aisle 
is  here  broken  up,  on  the  plan  instituted  at  Aachen,  into  alternately  triangular 

25 


26         THE   CONSTRUCTION  OF  LOMBARD  AND  GOTHIC   VAULTS 

spaces,  by  transverse  arches  (Fig.  49).  The  rectangular  spaces  are  covered  with 
sHghtly  domed  groin  vaults,  which  cover  the  wall  and  transverse  ribs  towards 
their  springing.  These  vaults  seem  to  have  been  constructed  without  solid  center- 
ing, precisely  like  the  ambulatory  vaults  above  described.  Although  the  ribs 
disappear,  they  probably  have  a  structural  function. 

In  the  church  of  S.  Tommaso  of  Almenno  the  side  aisle  and  gallery  are  both 
vaulted.  In  the  side  aisles  transverse  arches  reach  from  each  capital  to  the  side 
aisle  responds.  Those  arches  are  much  stilted,  as  are  also  the  arches  of  the  main 
arcade;  the  wall  arches,  supplied  with  ribs,  are  much  depressed;  the  groins  are 
also  depressed  and  sometimes  curved  in  plan  (Fig.  50).  Obviously  a  distorted 
and  awkward  surface  such  as  this  could  only  have  been  vaulted  by  the  use  of  a 
solid  board  centering,  and  in  this  case  the  traces  of  this  centering  are  still  clearly 
preserved  in  the  plaster.  The  transverse  ribs,  which  tend  to  die  away  towards 
the  springing,  and  the  wall  ribs  must  have  had  a  merely  decorative  purpose.  In 
the  gallery  (Figs,  51,  52)  the  vaults  are  of  a  different  type,  being  inclined  out- 
wards. This  very  probably  was  done  partly  to  buttress  the  dome,  partly  to  adapt 
their  extrados  to  the  form  of  the  roof  it  must  carry.  The  capitals  of  the  responds 
are  placed  lower  than  those  of  the  columns  facing  the  nave,  so  that  the  transverse 
ribs  acquire  a  curiously  distorted  form.  The  wall  rib,  being  much  depressed,  has 
its  crown  at  a  level  much  lower  than  that  of  the  transverse  and  arcade  arches. 
By  a  distortion,  apparently  made  purposely,  though  its  reason  is  difficult"  to  under- 
stand, the  highest  point  of  the  transverse  arches  is  thrown  at  a  point  nearer  the 
outer  than  the  inner  wall.  The  groins,  however,  though  broken,  tend  to  inter- 
sect at  a  point  which  is  very  near  the  inner  edge  of  the  vault.  The  transverse 
arches  thus  seem  to  sink  into  the  surface  of  the  vault  at  its  outer  edge,  and  would 
be  totally  submerged,  were  not  the  space  hollowed  out,  as  it  were,  to  receive  them. 
The  vaults  here  too  bear  undoubted  signs  of  having  been  erected  on  a  wooden 
centering.  How  difficult  to  erect  and  expensive  such  a  centering  must  have 
been,  even  in  a  small  edifice  situated  in  a  region  where  wood  was  abundant,  need 
not  be  insisted  upon. 

Vaults  of  this  type  were  carried  to  their  perfection  in  the  galleries  of  the  tran- 
sept of  S.  Fedele,  Como  (Fig.  53),  where  the  sloping  vaults  are  used  in  connection 
with  compartments  alternately  triangular  and  rectangular,  as  in  the  Rotonda  of 
Brescia.  But  the  transverse  arches  are  not  distorted,  their  inner  extrados  being 
loaded  to  bring  them  up  to  the  level  of  the  sloping  vaults.  The  vaults  are 
extraordinarily  thin,  being  only  six  inches  in  thickness,  and  were  doubtless 
constructed  in  this  manner  to  make  it  possible  to  lay  the  slates  of  the  roof 
directly  upon  them,  as  well  as  to  transmit  to  the  outer  walls  the  thrust  of  the 
great  half  domes  of  the  transept  ends.  They  were  erected  with  solid  centering; 
indeed  it  is  very  rarely  that  the  builders  of  the  province  of   Como  dispensed 


Fig.  -17.      S.  Stefano,  Verona.      Ambulatory  of  crvpt. 


Fig.  48.      S.  Stefano,  Verona.      .\!iilnil:it()ry. 


Fig.  49.      Duomo  Vecchio,  Brescia.     Side  aisle. 


Fig.  50.     S.  Tommaso,  Almenno  S.  Salvatore, 
(Bergamo).      Side  aisle. 


Fig.  51.      S.  Tommaso,  -Vliueiino  S.  Salvatore,  (Bergamo).      Gallery. 


I 


Fig.  54.      S.  Tommaso,  .Mmenno  S.  Salvatore, 
(Bergamo).      Gallery. 


Fig.  5-t.      S.  Pictro,  Asti,  (Alessandria). 


Fig.  53.      S.  Fcilele,  C'omo.      Gallery  of  north  Transept. 


/■ 


KiG.  55.      S.  Flaviano,  Montefiascone,  (Roma).      \aults  of  north  .side  aislf 


Fig.  56.       Cattedrale,  Aversa,  (Caserta).      Ambulatory.  Fig.  57.      S.  Sepolcro  at  S.  Stcfano,  Bologna.      Side  aisle. 


APPENDIX  27 

with  this  aid.  These  are  the  most  elegant  annuhir  vaults  of  the  Romanesque 
period  extant  in  Lombardy. 

In  S.  Pietro  of  Asti  we  have  a  ehurcli  which  shows  in  its  ornamental  features 
considerable  influence  of  the  school  of  Milan.  The  vaults  of  the  annular  aisle 
were  not,  however,  supplied  with  diagonal  ribs.  The  arches  of  the  main  arcade 
and  of  the  transverse  ribs  are  stilted  and  die  away  in  their  lower  i)arls;  the  groins 
become  correspondingly  sharply  accentuated  as  they  approach  the  supporting 
capitals.  The  number  of  sui)ports  is  equal  in  the  exterior  and  interior  j)crimeter. 
The  vaults  have  been  modernized,  but  the  very  shape  of  the  compartmenls  proves 
that  they  could  not  have  been  erected  without  solid  centering  (Fig.  54). 

Doubtless  of  entirely  similar  construction  were  the  vaults  of  the  aisle  of  San 
Sepolcro  (Santo  Stefano)  at  Bologna  (Fig.  57),  but  these  two,  unfortunately,  have 
been  made  over  to  such  an  extent  that  it  is  impossible  to  determine  their  original 
form.  Owing  to  the  irregular  plan  of  this  edifice,  the  compartnu>nts  to  be  vaulted 
are  more  irregular  than  those  at  S.  Pietro  of  Asti,  and  certainly  a  solid  centering 
must  have  been  employed. 

From  these  instances  it  will  be  seen  that  the  Lombards  never  succeeded  in 
erecting  groin  vaults  over  annular  galleries  or  ambulatories  without  centering, 
except  when,  as  in  Santo  Stefano  of  Verona  or  the  Rotonda  of  Brescia,  they  had 
recourse  to  the  expedient,  not  particularly  successful,  of  dividing  the  space  to  be 
vaulted  into  compartments  alternately  rectangular  and  triangular.  When  this 
was  not  done  it  was  necessary  to  employ  a  solid  centering.  However,  by  the  use 
of  ribs  it  was  possible  to  erect  vaults  over  a  trapezoidal  space  without  the  use  of 
centering. 

To  the  extent  of  my  knowledge  there  is  extant  in  Northern  Italy  no  example 
of  the  use  of  diagonal  ribs  to  simplify  the  construction  of  annular  vaults.  That 
is  not  to  say,  however,  that  such  a  construction  was  never  employed.  At  least  in 
Southern  Italy,  in  edifices  evidently  built  in  more  or  less  exact  imitation  of  Lom- 
bard models,  the  desire  to  economize  centering  in  the  erection  of  vaults  over 
annular  aisles  seems  to  have  led  to  the  adoption  of  rib  vaults  in  two  important 
instances,  the  cathedral  of  Aversa  and  S.  Flaviano  of  Montefiascone.  In  both, 
when  the  ribs  had  once  been  constructed,  the  remainder  of  the  vault  was  erected 
by  the  aid  of  a  simple  cerce.  Such  a  method  of  construction  was  doubtless  far 
easier  and  less  expensive  than  a  solid  centering,  especially  in  a  country  where 
wood  was  scarce.  In  these  early  examples,  which  make  one  think  of  the  early 
transitional  vaults  of  France,  the  builders  had  not  skill  enough  to  make  the  most 
possible  out  of  the  system.  At  Aversa  (Fig.  56)  the  ribs  are  straight  in  plan, 
hence  intersecting  out  of  center,  enormously  heavy,  and  the  whole  construction 
is  clumsy.  The  later  ambulatory  of  Montefiascone  (Fig.  ^^H)  introduces  trian- 
gular compartments,  has  ribs  which  are  broken  in  plan  and  much  lighter,  some 


28  THE   CONSTRUCTION   OF  LOMBARD  AND   GOTHIC  VAULTS 

even  being  given  a  round  profile.  The  builders  had  evidently  progressed  some  dis- 
tance on  the  road  which  leads  towards  Gothic,  but  no  further  experiments  along 
this  line  seem  to  have  been  made  in  Italy. 

Corneto-Tar([uinia  (Provincia  di  Roma)  affords  another  interesting  example 
of  the  use  of  ribs  to  economize  centering  in  the  erection  of  a  vault.  Ribs  were 
applied  to  the  half  dome  of  the  apse  of  Santa  Maria  di  Castello  (Fig.  G2).  These 
ribs  once  built,  the  remainder  of  the  vault  could  be  constructed  without  further 
centering,  for  in  this  case  the  ribs  tend  to  converge  towards  the  key-stone  where 
the  construction  became  more  difficult.  The  same  expedient,  it  will  be  recalled, 
was  resorted  to  by  the  builders  of  Northern  France  (Fig.  59).  The  French 
builders,  to  facilitate  the  placing  of  the  windows,  gradually  lobed  and  raised  the 
compartments  until  the  Gothic  chevet  vault  resulted.  But  in  Italy  this  step 
was  never  taken. 

In  the  church  of  S.  Pancrazio  at  Corneto  is  a  sexpartite  vault  (Figs.  58,  60). 
This  church  is  of  a  single  aisle  and  very  wide,  being  almost  square  in  plan.  Con- 
structing in  stone  without  solid  centering,  the  builders  did  not  dare  attempt  to 
cover  the  entire  church  with  a  single  great  rib  vault.  They  therefore  divided  it 
into  two  oblong  compartments.  But  even  so  the  size  of  the  spaces  and  the  flat- 
ness of  the  surfaces  dismayed  them,  so  they  determined  to  erect  an  intermediate 
transverse  arch.  They  thus  obtained  nearly  vertical  surfaces  for  almost  the  entire 
extent  of  the  two  great  compartments,  the  length  of  the  courses  of  which  had 
offered  difficulties.  This  vault,  however,  shows  merely  the  hesitation  of  inex- 
perience. Wishing  to  economize,  the  builders  in  the  end  erected  a  vault  probably 
almost  as  expensive  as  if  they  had  used  solid  centering.  The  experiment  was  not 
repeated.  Even  in  the  western  bay  of  this  same  church  there  is  substituted  a 
transverse  arch  in  three  spans  supporting  a  wooden  roof  in  place  of  the  similar 
vault  it  was  doubtless  the  intention  to  erect. 

The  philosophy  of  this  vault  is  therefore  in  part  different,  in  part  similar,  to 
that  of  the  sexpartite  vaults  of  Northern  France  (Fig.  61).  There  the  builders 
were  moved  not  so  much  by  timidity  as  by  the  desire  to  economize  centering. 
Just  as  the  Lombards  preferred  to  vault  their  naves  on  square  plans  with  an  alter- 
nate system,  dispensing  thus  with  three  superfluous  centering  arches,  the  French 
adopted  an  alternate  system  with  nave  vaults  embracing  two  bays.  But  they 
carried  their  logic  of  economy  farther.  If  all  the  weight  of  the  vaults  was  to  be 
concentrated  on  the  alternate  piers,  these  had  to  be  made  unduly  heavy,  and  the 
intermediate  piers,  even  though  lightened,  failed  to  receive  all  the  charge  they 
were  capable  of  carrying.  Such  a  lack  of  economy  was  repellent  to  the  logical 
spirit  of  the  French  builders.  To  remedy  it  they  introduced  even  at  the  expense 
of  additional  centering  an  extra  intermediate  transverse  arch.  Thus  they  suc- 
ceeded in  covering  a  double  bay  by  the  aid  of  nine  centering  arches  instead  of  the 


Fig.  58.      S.  Pancrazio,  Cometo-Tarquinia,  i,Uoma).      Vault  of  Nave. 


Fig.  59.      St.  Rerai,  Brujere-sur-Fere,  (Aisne). 
Choir  and  Apse. 


Fig.  CO.      S.  Pancrazio,  Cometo-Tarquinia,  (Roma). 


Fig.  61.      S.-Etienne,  Caen,  (Calvados).      Nave  vaults. 


^^K^ 

|- 

I, 

*• 

1 

i- 

. 

Jli 

4 

r' 

^1 

Hi 

m- 

* 

il 

»« 

_.     ^ 
t 

Fig.  6i.      S.  Maria  di  Castello,  Cormlo-Tanjuinia, 
(Roma).     Apse. 


Fig.  G3.      S.  Fe  al  Po,  Cavagnolo,  (Torino). 


APPENDIX  29 

eleven  that  would  be  necessary  for  a  vault  erected  on  a  uniform  system.  Further- 
more, four  of  the  six  compartments  consisted  of  sharply  inclined  surfaces  the 
courses  of  which  it  was  easy  to  construct  with  the  aid  of  a  cerce.  The  alternate 
piers  were  relieved,  moreover,  of  a  disproportionate  share  of  the  charge.  For 
these  reasons,  the  sexpartite  form  was  preferred  in  France  during  the  XII 
century,  although  the  quadripartite  oblong  form  was  perfectly  well  known  to  the 
builders.  It  will  be  recalled  that  St.-Etienne  of  Beauvais,  where  the  nave  was  rib 
vaulted  in  oblong  compartments,  antedates  St. -Denis,  the  earliest  example  of 
sexpartite  vaults  in  the  Ile-de-France. 

The  sexpartite  form  in  France  was  probably  abandoned  because  the  great 
length  of  the  diagonals  raised  the  crown  of  the  vaults  to  such  a  height  that  it 
became  necessary  to  raise  correspondingly  the  walls  so  that  the  roof  should  clear 
them.  This  raising  of  the  walls  wasted  material,  and  moreover  increased  the 
weight  that  must  be  carried  by  the  piers;  so  the  builders  concluded  that  it  was 
better  to  return  to  the  uniform  system  even  at  the  expense  of  erecting  two  more 
centering  arches  for  their  vaults. 

Centering  was  always  used,  so  far  as  I  am  aware,  in  the  erection  of  barrel 
vaults  in  Lombardy,  and  these,  it  will  be  recalled,  were  regularly  used  in  the 
choirs  and  transepts.  Santa  Fe  of  Cavagnolo,  Torino  (Fig.  63),  even  has  a  nave 
completely  barrel-vaulted.  In  France  as  well,  in  the  full  Gothic  period,  certain 
vaults  were  undoubtedly  erected  with  solid  centering.  But  although  the  medieval 
builders,  whether  in  Italy  or  in  France,  never  went  as  far  as  the  Byzantine  builders 
in  their  efforts  to  dispense  with  temporary  wooden  structures,  and  always  con- 
tinued to  use  even  a  solid  centering  in  certain  contingencies,  nevertheless  the 
desire  to  build  vaults  without  a  cumbrous  and  expensive  centering  in  wood  was 
a  guiding  principle  in  the  development  of  architecture  in  Lombardy  and  France 
in  the  XI  and  XII  centuries,  and  was  the  chief  if  not  the  sole  motive  that 
led  to  the  introduction  of  the  rib  vault. 


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